DEFINITION OF 'MONTHLY WAGES' AS CONTEMPLATING OR NOT OVERTIME PAY FOR SPECIFIC HOLIDAYS AND CONTRIBUTIONS BY EMPLOYER TO HEALTH AND WELFARE FUND. Where labor agreement can be opened for renegotiation and review of "monthly wages," subject of overtime pay for specific holidays is open to equal consideration, but subject of employer contributions to health and welfare fund is not; former being included within meaning of "monthly wages" and latter being excluded.