15. If you are the boss of McDonalds and you have four personnel. Mr. FLY can produce 48 burgers within eight hours per day. Mr. JOY can produce 54 burgers within ten hours per day. Mrs. STAR can produce 63 burgers within 12 hours per day. Mrs. LUCKY can produce 72 burgers within 15 hours per day. According to the economic productivity theory, who should be honored by the highest productivity:
(A) Mr. FLY,
(B) Mr. JOY,
(C) Mrs. STAR,
(D) Mrs. LUCKY,
(E) Four persons all equal.