MR. CHIEF JUSTICE TURNAGE delivered the Opinion of the Court

Claimant appeals an order of the Workers' Compensation Court offsetting his state workers' compensation disability pay by 50 percent of his entire weekly federal disability pay. The issues on appeal are (1) whether the lower court erred in determining that the workers' compensation offset statute, Section 39-71-702(2), MCA (1981), was clear and unambiguous on its face; (2) whether the lower court erred in denying Watson attorney fees and costs; (3) whether Watson is entitled to have the statutory penalty of 20 percent assessed against defendant State Fund for unreasonable delay or failure to pay a claim; and (4) whether Watson can argue on appeal that the lower court's construction of the offset statute is unconstitutional when he did not advance that argument at the trial level. We affirm

On August 31, 1979, appellant, age fifty-six, suffered an industrial accident while working for defendant Seekins which rendered him totally permanently disabled. He then began receiving state disability benefits from the Workers' Compensation State Fund. He was receiving $198.00 per week from the State Fund in 1985. On January 30, 1985, appellant Watson turned sixty-two years old and shortly thereafter applied for early retirement benefits from the Social Security Administration. These monthly benefits, payable at $261.00 per month were lower than full retirement benefits available from Social Security had he chosen to postpone retirement until age sixty-five

After receiving early retirement benefits for about six months, Watson changed his mind and applied for disability benefits instead. The disability pay was a larger monthly amount but was also subject to the state setoff statute, Section 39-71-702(2), MCA (1981). Watson's election of disability pay was accepted by the Social Security Administration, and he began receiving $372.00 per month, an increase of $111.00 per month over the early retirement pay. He also received a lump sum payment of back benefits for disability dating back to the date when he actually turned sixty-two. This back payment effectively made his election to take disability retroactive and eliminated his election to retire early

In a letter dated August 4, 1986, the Workers' Compensation Division notified Watson that it would be applying the setoff allowed by statute to his weekly disability benefits received from the state government. The setoff (50 percent of his weekly federal benefits) would be deducted from his weekly state disability benefits in order to eliminate the duplication of disability pay. The Division also claimed an overpayment in the amount of $3,461.62, which it wished to recover from Watson

The result was that Watson suffered a reduction of $42.81 per week from his state disability pay and actually received less monthly money overall due to the setoff than he would have had he stuck with his original election of early retirement

The Division's computations were as follows:

Step 1

monthly which weekly $372.00 federal resolves $ 85.62 federal disability itself to disability

Step 2

weekly $ 85.62 federal reduced by 50% = $ 42.81 setoff disability rate

Step 3

weekly weekly $198.00 state — $42.81 setoff = $155.19 workers' workers' compensation compensation

Watson challenged those computations. He argued that the entire amount of $372.00 disability pay should not be subject to setoff Rather, he argued, only the $111.00 difference between retirement pay and disability pay should be subject to setoff. Watson argued that he was entitled to retirement pay of $261.00 in his own right which was not subject to setoff and, therefore, only the increased amount of $111.00 could be used in the setoff computations. Under Watson's theory, he would suffer a weekly reduction in state money of only $12.78

Defendant State Fund argued that the election was a choice entitling Watson to one benefit or the other, but not both. If Watson chose to take disability pay, that pay (the entire amount) was subject to the state statute allowing setoff. State Fund found the statute in question to be plain and unambiguous, stating that where disability pay is given by the federal government it is subject to setoff by the state government

The Workers' Compensation Court adopted the findings of fact and conclusions of law as determined by the Hearing Examiner and entered its judgment and order on December 21, 1987. The court determined the statute to be clear and unambiguous on its face, affecting the entire amount of federal benefits. Its order provided that the defendant was entitled to an offset in the amount of $42.81 per week based on the entire weekly disability benefits paid to Watson under the Social Security Act. It further found that such an offset would continue for as long as Watson received federal disability pay and that he was neither entitled to the requested attorney fees and costs, nor a 20 percent penalty against the Division for unreasonable refusal or delay in payment. Watson's January 7, 1988, motion for a new trial was denied, and this appeal followed

Watson's primary issue on appeal is that of statutory construction and legislative intent. Appellant argues that the court misinterpreted the statute; that the statute is ambiguous in that it is susceptible of two interpretations; that where a genuine doubt exists, the ambiguity should be resolved in favor of the injured claimant; and finally that accepting the court's interpretation of the statute would be an unconstitutional violation of the Supremacy Clause, in that it would nullify the effect of the federal disability provisions of the Social Security Act for persons such as Watson

This Court finds the statute to be clear and unambiguous, affirming the Workers' Compensation Court judgment. Affirmation of the lower court on the merits of the first issue renders the remaining issues of the attorney fees, costs and penalty moot

I. INTERPRETATION OF THE STATUTE

The offset statute is Section 39-71-702(2), MCA (1981). This statute was amended in 1987 and its successor is Section 39-71-702(4). However, it is the statute in effect at the time of the injury that sets the standard by which the benefits to the claimant are to be computed. Trusty v. Consolidated Freidgtwasy Mont. 1984), [ 210 Mont. 148,] 681 P.2d 1085, 41 St.Rep. 973. That statute reads in pertinent part as follows:

"In cases where it is determined that periodic disability benefits granted by the Social Security Act are payable because of the injury, the weekly benefits payable under this section [under the state Workers' Compensation Act] are reduced, but not below zero, by an amount equal, as nearly as practical, to one-half the federal periodic benefits for such week, which amount is to be calculated from the date of the disability social security entitlement."

Watson argues that the language, payable because of the injury, refers only to the increased amount of $111.00 per month, which is the difference between the early retirement amount and the disability amount. It is his statutory construction that this is the only "fair" way to read the statute and that any other interpretation is perverse. We disagree

All statutory construction by courts is an attempt to search out the intent of the legislature. Johnson v. Marias River Electrical Cooperative, Inc. (Mont. 1984), [ 211 Mont. 518,] 687 P.2d 668, 41 St.Rep. 1528. This Court's role, then is to let the legislative intent control whenever possible. Darby Spar, Ltd v. Dept. of Revenue (Mont. 1985), [ 217 Mont. 376,] 705 P.2d 111, 42 St.Rep. 1262

Watson argues his interpretation is the only fair one because it is the one construed consistently with the legislative intent According to Watson, the legislative intent is to benefit disabled workers more than merely retired workers. Watson cites Freeman v. Harris (5th Cir. 1980), 625 F.2d 1303, and Lindquist v. Brown (8th Cir. 1987), 813 F.2d 884, as authority for construing a statute in favor of the claimant by using legislative intent. However, these cases are of little help in determining the legislative intent for the Montana statute in question

The Freeman case is not dispositive on this issue and is only similar to the case at bar in that the Freeman court interpreted the legislative intent espoused in two federal offset statutes. In Freeman the claimant received benefits from three sources: federal Social Security, state workers' compensation and federal Black Lung benefits. Because both the workers' compensation and Social Security were offset against the Black Lung award, the claimant ultimately received less under the three programs than he would have under only two programs not so heavily offset

However, the distinction here is that the federal black lung statute required the claimant to simultaneously pursue state workers' compensation funds which triggered the double offset The court found the congressional intent expressed in the Social Security Act was that the states would be the primary providers of disability benefits to workers and that the federal government would only assist where state programs were inadequate. The result under double offset was to discourage injured miners from seeking state workers' compensation benefits. That result contravened the congressional intent. Additionally, the court found the corresponding legislative intent behind the Black Lung statute was to replace income for injured workers. These two legislative goals could not be met simultaneously in the Freeman case Thus, the court resolved the tension by letting both offsets stand as authorized by statute but not so as to exceed 100 percent of the state workers' compensation benefits payable to claimant

These facts do not help us resolve the question of legislative intent for our statute. The required double offset in Freeman is not analogous to the elective single offset under these facts Moreover, our statute has already considered the ultimate issue decided in Freeman, that the offset cannot be 100 percent of the benefit, or in the language of the Montana statute, "cannot reduce the benefit below zero."

Likewise, Lindquist is not helpful in the instant case merely because the Lindquist court declared the legislative intent behind the Social Security retirement pay schedule was to encourage people to continue working and postpone retirement

Claimant also asserts Subsequent Injuries Fund v. Industrial Accident Commission (1963), 217 Cal.App.2d 322, 31 Cal.Rep 508, as authority for "pro rating" the federal Social Security benefits. By statute, California maintained a fund to compensate industrial injuries which were aggravations of a preexisting injury. The legislative intent was to encourage injured workers to rehabilitate and re-enter the work force. The plaintiff in that case went blind as a result of an industrial accident. It was determined that the resultant blindness was caused 68.25 percent by the preexisting injury. Thus, the Fund was allowed to reduce its payments by 68.25 percent of the Social Security benefits awarded

However, that California case on quite different facts is not persuasive authority to pro rate Watson's federal benefits and find that 70 percent of his pay is due to retirement and 30 percent is due to injury. We are not inclined to read that into the Montana statute on the basis of a California "pro rata" case interpreting a statute with a totally different legislative intent

The legislative intent behind the workers' compensation statutes is to replace income to injured workers. The purpose behind the state offset statute is to prevent "over replacement" or duplication of disability pay. Offset has never applied to federal retirement pay

Everyone is in agreement that under the Montana statute where federal disability benefits are awarded, state setoff occurs. The dispute is how much disability pay should be used to compute setoff: all of it or only part of it. The statute simply does not allow for Watson's formula to exclude a part of the entire award The words are not there. The role of the Court is not to insert what has been omitted by the statute. Chennault v. Sager (1980), 187 Mont. 455, 610 P.2d 173. Had the legislature intended an exemption, exclusion, or any other formula to apply to reduce the amount subject to setoff, it is reasonable to assume that it would have expressed it in the statute

It should be noted here that Watson did not submit evidence that the legislature intended only the difference between the two amounts be considered as disability benefits. Nor did Watson show that the statute had ever been interpreted that way in the past Absent such evidence, the Workers' Compensation Court properly was reluctant to change the plain reading of the language in order to effect claimant's wishes. Additionally, this Court finds no such evidence in the legislative history of the statute

Therefore, we conclude that the language in the statute, "payable because of the injury," is not an authorization for the exemption of a part of Watson's federal disability from the state setoff. Thus, the statute is not susceptible of two meanings, and no ambiguity exists

Lastly, we find that the lower court's interpretation of the statute is not an unconstitutional violation of the Supremacy Clause

Watson is allowed to advance that argument on appeal when he did not specifically raise it at trial because it is not meant to be an independent constitutional challenge to the statute Rather, it is an attack on how the lower court construed the statute, which is an inherent theory to his primary argument: that the court erred in interpreting the statute. American Equitable Assurance Co. v. Newman (1957), 132 Mont. 63, 313 P.2d 1023, 1027

However, Watson's theory is without merit. The state statute does not prohibit Watson from electing to take federal disability pay nor does it preclude him from receiving that pay to which he is entitled under the federal act. Thus, it does not nullify the federal statute. Therefore, the Montana statute as interpreted by the lower court is constitutional

It is, however, a likely disincentive for injured workers between ages sixty-two and sixty-five to elect to take the federal funds subject to setoff. As in Watson's case, his choice did not benefit him in the end

We have considered the statute in question, along with the arguments and authorities advanced by counsel. We conclude that the statute is clear and unambiguous in its plain language Whether the plain interpretation of this statute is unfair under the particular facts of the Watson case is, regrettably, not for the judiciary

Judgment affirmed

MR. JUSTICES HARRISON, McDONOUGH and GULBRANDSON concur