求解2道PREP数学题

（一）Store S sold a total of 90 copies of a certain book during the 7days of last week, and it sold different numbers of copies on any 2 of the days. If for the 7 days store S sold the greatest number of copies on Saturday and the second greatest number of copies on Friday. Did Store S sold more than 11 copies on Friday?

1) Last week store S sold 8 copies of the book on Thursday.

2)Last week store S sold 38 copies of the book on Saturday.

correct answer:B

（二）A store purchased 20 coats that each cost an equal amount and then sold each of the 20 coats at an equal price.What was the store's gross profit on the 20 coats?

1)If the selling price per coat had been twice as much, the store's gross profit on the 20 coats would have been $2400.

2)If the selling price per coat had been $2 more, the store's gross profit on the 20 coats would have been $440.

correct answer:B

我第二题看不懂题，不是要求总的gross profit 吗？1和2都已经给出了gross profit了啊，还要怎么算啊？

请CDer们帮我指点一下吧，非常感谢！！！

我也搞不懂。望指点

第一题 1给出了周四的销售量 无法确定周五具体销售了多少

       2 给出周六销售了38件 余下的六天一共销售了（90-38=52)件， 假设周五销售了11件，由于周五是销售件数第二多的，所以除了周六和周五其余的五天件数由大到小为10，9，8，7，6。11+10+9+8+7+6=51<52 因此周五那一天销售件数一定是大于11件的  因此选B

第二题 假设该商店外套的成本价为X 销售价为Y  商店销售20件的毛利为20（Y-X)

由1得 20（2Y-X)=2400  得不到Y-X的具体数值

由2得 20（Y+2-X）=440 的得到Y-X为20 因此选B