单项选择题

A.lx=(150+875+636)×2+3900+2×2.29×18+4×0.67×18=7353
B.lx=(150+875+636)×2+3900-2×2.29×18-2×0.67×18=7115
C.lx=(150+875+636)×2+3900-4×0.67×18=7174
D.lx=(150+875+636)×2+3900+2×2.29×18-2×0.67×18=7280