It has also been generally recognized that the burden of establishing facts in mitigation of the back pay liability is upon the unfair labor practice violator, and not upon the General Counsel of the Board who represents the interests of the discriminatee. See Alaska Steamship Co., 114 NLRB 1264, 1265 (1955), aff'd., 245 F.2d 282 (9th Cir. 1957); Southern Silk Mills, Inc., 116 NLRB 769, 773 (1956), remanded, 242 F.2d 697 (6th Cir.), cert. denied, 355 U.S. 821, 78 S.Ct. 28, 2 L.Ed.2d 37 (1957); Florence Printing Co. v. N.L.R.B., 376 F.2d 216, 221, (4th Cir.), cert. denied, 389 U.S. 840, 88 S.Ct. 68, 19 L.Ed.2d 104 (1967); N.L.R.B. v. Brown Root, Inc., 311 F.2d 447, 452 (8th Cir. 1963). Once the General Counsel has established the gross amount of back pay due the discriminatees in question, "the burden is upon the employer to establish facts which would negative the existence of liability to a given employee or which would mitigate that liability."

f the Company president's explanation that Frank and Aguiar would have continued in their journeymen status on the Rhode Island Hospital job and on other work except for Union pressure. Respondents also contend that reinstatement is a condition precedent to the Board's authority to compel a back pay award but as was said in National Labor Relations Board v. Local 1423, etc., 5 Cir., 1956, 238 F.2d 832, this argument is foreclosed by the decision in Radio Officers' Union of Commercial Telegraphers Union, A.F.L. v. National Labor Relations Board, 1954, 347 U.S. 17, 74 S.Ct. 323, 98 L.Ed. 455. Bearing in mind that a back pay order of the Board "should stand unless it can be shown that the order is a patent attempt to achieve ends other than those which can fairly be said to effectuate the policies of the Act", National Labor Relations Board v. Seven-Up Co., 1953, 344 U.S. 344, 347, 73 S.Ct. 287, 289, 97 L.Ed. 377; see National Labor Relations Board v. Alaska Steamship Co., 9 Cir., 1957, 245 F.2d 282, we find no merit in the respondents' other contentions concerning the back pay order. The respondents' contention that the Company should be required to contribute toward making Frank and Aguiar whole also lacks weight in view of the holding in Radio Officers' Union of Commercial Telegraphers Union, A.F.L. v. National Labor Relations Board, supra, 347 U.S. at page 52, 74 S.Ct. at page 342.