We believe that the trial court was correct in its conclusion that the contract was a "unit contract" and not a "lump sum" contract and that respondents were entitled to be paid for the amount of actual work installed at the unit price. A case closely in point is Frazer v. City of Ardmore, 103 Okla. 31 [ 229 P. 143]. In that case, the city approved plans and specifications and estimates for street paving, detailing therein the quantities of the several items necessary to go into the improvement together with the cost per item, amounting in the aggregate to the sum of $20,076.51.
The foregoing statements of the law, save and except where otherwise stated herein, refer to contracts where the compensation is fixed at a lump sum, and under such circumstances we find that immaterial changes or modifications which do not substantially affect the character of the work or unreasonably increase the cost thereof, are permissible. In the case of Frazer et al. v. City of Ardmore, 103 Okl. 31 [ 229 P. 143], we have a case on all-fours with the one at bar. There, the contract was based upon a unit price of the work to be performed in determining the compensation that would be earned by the contractor.
" To the same effect see Loomis Fruit Growers Association v. California Fruit Exchange (Cal.App.) 16 P.2d 1040; Wiebener v. Peoples, 44 Okla. 32, 142 P. 1036; Frazier v. City of Ardmore, 103 Okla. 31, 229 P. 143; Minnetonka Oil Co. v. Cleveland Vitrified Brick Co., 27 Okla. 180, 111 P. 326; Rider v. Morgan, 31 Okla. 98, 119 P. 958. In the case of Gladys Bell Oil Co. v. Clark, 147 Okla. 211, 296 P. 461, this court states:
Parol evidence was inadmissible to vary its terms. The case is ruled by the decision of this court in Frazer v. City of Ardmore, 103 Okla. 31, 229 P. 143, where a similar contract was under consideration. The contract in that case contains a provision that the contractor should receive the sum of $ 19,915.
Defendant contends that under the terms of the contract he is entitled to charge this item to plaintiff, but the trial court held against defendant by sustaining a motion to strike from his answer the allegations relating to said payment. Defendant takes the position that the contract is ambiguous, uncertain, and contradictory in its terms, and susceptible of two constructions in connection with the liability of defendant to pay the ground rentals during the time he remained in possession; that the lease was assigned to him in his capacity as a broker for the sole purpose of facilitating a sale, and on account of the ambiguity of the contract he is entitled to plead and prove that, in the contemplation of the parties, there was no intention that he should be responsible for ground rentals to the owner during his term of possession, citing Quinette v. Mitschrich, 109 Okla. 281, 235 P. 530; Frazer v. City of Ardmore, 103 Okla. 31, 229 P. 143. It is a cardinal rule in the construction of a contract that the language governs its interpretation, if the language is clear and explicit and does not involve an absurdity.
Section 5040, C. O. S. 1921. The meaning thereof might be shown by the construction placed thereon by the parties thereto. Knebel v. Rennie, 87 Okla. 136, 209 P. 414; Frazer v. City of Ardmore, 103 Okla. 31, 229 P. 143; R. T. Stuart Co. v. Graham, 117 Okla. 117, 245 P. 608; Grain v. Pure Oil Co., 25 F.2d 824, and Baker Strawn v. Butler, 141 Okla. 9, 283 P. 556. Effect must be given to the intention of the parties (section 5039, C. O. S. 1921), and the intention of the parties may be ascertained in the manner provided by article 3, ch. 32, C. O. S. 1921. The record shows nothing tending to vary the terms of the written contract by parol evidence, although there was much evidence offered that tends to explain the meaning of the ambiguous portion of the contract.