prescribe reasonable minimum standards for benefit plans offered under this chapter. (b) (1) Benefits provided to an employee under this chapter shall offset other benefits received by such employee for the same injury or disability, leave to care for or make arrangements to care for a member of family (including the birth of a son or a daughter), or leave to make arrangements to adopt a child or become a foster parent including worker’s compensation and disability retirement income. (2) A contract providing benefits under this chapter— (A) shall not provide for a preexisting condition exclusion