Roller skates cost a retailer $120.00 less 20%, 10%. The retailer sold them for $150.00. What was the rate of mark-up on cost?

A) 20%
B) 44%
C) 55%
D) 73.6%
E) 42.4%

Ross's compensation is to be changed from an hourly rate of $15.75 for a 40-hour week to a salary paid semimonthly. What should he be paid semimonthly in order for his annual earnings to remain the same?