The Milwaukee County Juvenile Detention Center established a new policy that required each unit of the facility to be staffed at all times by at least one officer of the same gender as the detainees housed at a unit. The purpose of the policy, administrators said, was to reduce the likelihood of sexual abuse of juveniles by officers of the other gender. Because there were many more male units in the center than female units, the policy had the effect of reducing the number of shifts available for women officers and increasing the number of shifts for men. Two female officers sued for gender discrimination. The district court held for the county, finding that the policy of assignment was based on a bona fide occupational qualification (BFOQ) and so was not illegal gender discrimination. The officers appealed. What would be evidence that the county had a valid BFOQ?