求解一道题

7-11

A certain sporting goods retailer gets a shipment of x bicycles each month. It is estimated that the retailer keeps half a shipment of bicycles in storage at all times. If the cost of storing a bicycle for one month is $0.25, approximately what is the reatailer's annual cost, in dollars, for storing bicycles?
(A)6x
(B)3x/2
(C)x
(D)x/4
(E)x/24

Answer: B
能否给个解题思路

conan0408

每月库存=X/2
每月库存cost=X/2*0.25=X/8
12个月csot=每月库存cost*12=X/8*12=3X/2

pattyx

a shipment是x辆车， half a shipment就是 x/2辆
每辆0.25刀/月，就是x/8刀每月
总共一年12个月，就是12x/8=3x/2

lprovence

怎么知道这个不是复利计息那种呢？