MADifferential piecework payment scheme - wages

Question) A differential piecework payment scheme operates in the packing department of a factory. Straight piece rate is $ 10 per unit. Details of the scheme are as follows: Units packed per week ------- premium rate per unit 1-2000 units per week ------- 50 cents per unit 2001 to 3000 units per week ------- 65 cents per unit 3001 to 4000 units per week ------- 75 cents per unit Only extra units packed, over the previous threshold, qualify for the higher rates. If 3240 units were packed, how much would be paid in wages?? A. $15,274 B. $ 24, 876 C. $ 30,000 D. $ 34, 230 I get D by calculating premium rates for 3240 units and adding in the standard ($ 3240 * $ 10). Is this solution correct??