Read this: Air Force officer promotions are governed by the Defense Officer Personnel Management Act of 1980 and its companion Reserve Officer Personnel Management Act (ROPMA) for officers in the Air Force Reserve and the Air National Guard. DOPMA also establishes limits on the number of officers that can serve at any given time in the Air Force. Currently, promotion from second lieutenant to first lieutenant is virtually guaranteed after two years of satisfactory service. The promotion from first lieutenant to captain is competitive after successfully completing another two years of service, with a selection rate varying between 99% and 100%. Promotion to major through major general is through a formal selection board process, while promotions to lieutenant general and general are contingent upon nomination to specific general officer positions and subject to U.S. Senate approval.

Who establishes limits on the amount of Air Force officers? 
What is the answer? (If it cannot be answered, return "unanswerable")
DOPMA