ACCA F2某细节问题

An organisation operates a piecework system of remuneration, but also. guarantees its employees 75% of a time-basedn rate of pay which is based on $19 per hour for an eight hour working day Three minutes is the standard time allowedper unit of output. Piecework is paid at the rate of $18 per standard hour.If an employee produces 200 units in eight hours on a particular day, what is the employee✀s gross pay for thatday?A $114B $152C $180D $190这一题我知道答案，但 这一句：guarantees its employees 75% of a time-basedn rate of pay which is based on $20 per hour for an eight hour working day不知道是什么意思