It is not an unlawful practice for an employer to apply different standards of compensation or different terms, conditions, or privileges of employment pursuant to a bona fide seniority or merit system, or a system which measures earnings by quantity or quality of production, or to employees who work in different locations, provided that such differences are not the result of an intention to discriminate because of race, color, religion, national origin, sex, disability, or age; nor is it an unlawful practice for an employer to give and to act upon the results of any professionally developed ability test, provided that such test, its administration, or action upon the results thereof is not designed, intended, or used to discriminate because of race, color, religion, national origin, sex, disability, or age.