If an employee during a workweek works in different capacities in
the performance of the contract and two or more rates of compensation
under section 2 of the Act are applicable to the classes of work which
he or she performs, the employee must be paid the highest of such rates
for all hours worked in the workweek unless it appears from the
employer's records or other affirmative proof which of such hours were
included in the periods spent in each class of work. The rule is the
same where such an employee is employed for a portion of the workweek in
work not subject to the Act, for which compensation at a lower rate
would be proper if the employer by his records or other affirmative
proof, segregated the worktime thus spent.