请教一道数学题，求各位NN们帮忙~

freddxy

At a certain supplier, a machine of type A costs $20,000 and a machine of type B costs $50,000.Each machine can be purchased by making a 20 percent down payment and repaying the remainder of the cost and the finance charges over a period of time.If the finance charges are equal to 40 percent of the remainder of the cost, how much less would 2 machines of type A cost than 1 machine of type B under this arrangement?



(A) $10,000

(B) $11,200

(C) $12,000

(D) $12,800

(E) $13,200

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【答案】E

【思路】Machine A:
 40000                down payment:8000
remainder:                                40000-8000=32000
finance charge: 12800                 total:40000（疑惑：这里应该是40000*0.8啊）+12800=52800
Machine B:                                             50000                down payment:10000
remainder:50000-10000=40000
finance charge: 16000
total:                                             50000（这里也有问题）+16000=66000
difference between two arrangement:66000-52800=

我觉得不对啊~ 条件1：Each machine can be purchased by making a 20 percent down payment and repaying the remainder of the cost and the finance charges over a period of time. 条件2：If the finance charges are equal to 40 percent of the remainder of the cost   那么总的花费应该是根据条件一repaying the remainder of the cost + the finance charges over a period of time      而finance charges是根据条件二   即总的花费=0.8*原价+0.8*原价*0.4 所以这样算来应该选B。求牛人帮忙！谢谢！可能我的逻辑不对。