A differential piecework scheme has a basic rate of $0.75 per unit. Output in addition to 500 units is paid at higher rates. The premiums over and above the basic rate, which apply only to additional units over the previous threshold, are: . Output (units) Premium (per unit) 501-600 $0.05 above 600 $0.10 What is the total amount paid if output is 800 units? Select one: O a. $625 O b. $800 O c. $680 O d. $400