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题库 / GMATAdvanced-CR-31
Clearbell Telephone provides slow-dialing (SD) service to customers for a low fee, and fast-dialing (FD) service to other customers who pay a somewhat higher fee. FD technology, however, is so efficient that it costs Clearbell substantially less per average call to provide than does SD. Nonetheless, accountants have calculated that Clearbell’s profits would drop if it provided FD to all its customers at the current low-fee rate.
Assume that installation costs for FD are insignificant if the customer already has SD service. Which of the following, if true about Clearbell, best explains the results of the accountants’ calculation?
The extra revenue collected from customers who pay the high fee is higher than the extra cost of providing SD to customers who pay the low fee.
The low fee was increased by 6 percent last year, whereas the higher fee was not increased last year.
Although 96 percent of customers regard FD service as reliable and more convenient than SD, fewer than 10 percent of them choose to pay the higher fee for FD service.
The company’s competitors generally provide business customers with FD service at low-fee rates.
Profits rose slightly each month for the first three months after FD was first offered to customers, then fell slightly each month for the succeeding three months.
B/C只知道单项数据没有意义
D. 看不出来competitors对它有啥影响 因为没有换之前也有competitors
E错： 只说了profit变化情况，但是没有说明原因
FD技术提高了，所以每个FD电话的成本比SD低了。
答案是，会计计算得出，C的收益会降低，如果所有客户都用FD服务，但收取低费用。
问在安装费不变的情况下，怎么解释？
猜想：Profit↑=revenue-cost↓
SD revenue低，FD revenue高
现在cost（FD）P (SD)，但是为什么如果都让客户用FD，profit反而会下降？注意这里影响both SD and FD，因为换成FD的技术之后，SD的收费还是不变的，但是FD收入下降了。
A：从付高费用的顾客得到的额外revenue比额外cost（SD）高。这里有一个很隐晦的点——
Profit（SD）=r（不变）-C↓
Profit（FD）=R（变成low fee）-C↓
所以这里无法判断cost下降了多少。也就无法判断profit增多或者减少。A说[R（FD）-R（变成low fee）]>[cost(SD)-cost↓]，这里明确了变化范围，所以ΔR > Δcost, 所以收入减少了。
A: 高费用获得的额外收入（降低的收入） 大于 低费用S所需的额外成本（未来会降低的成本）
降低成本的同时更多地收入没了.....profits下降 第一次看没看懂的我 能很快绕过来的好厉害
profit (FD)=收来的高费用 high fee - 付出的低成本 low cost
profit (SD)=收来的低费用 low fee - 付出的高成本 high cost
若FD改成SD，并且收low fee。 即，
新profit (FD)↓=收来的高费用 high fee（↓为low fee） - 付出的低成本 low cost
新profit (SD)↑=收来的低费用 low fee - 付出的高成本 high cost（↓为low cost）
所以，新profit (FD)下降↓，新profit (SD)上升↑
extra revenue collected from customers who pay the high fee ＞ extra cost of providing SD to customers who pay the low fee
从支付高额费用的客户那里收取的额外收入＞向支付低费用的客户提供 SD 的额外成本。
②现在accountants认为这换成FD之后利润会降低，分析：利润降低那就是收入降低>成本降低,所以题目让我们选出符合这种情况的。A选项（这种情况讲的是换之后相对于没换之前的变化，也就是extra，这两个extra之所以是“额外的”就是因为换了之后他们俩都没了，就是前面说的都降低了）那么A选项就可以理解成：消失的收入>消失的成本，也就是收入降低>成本降低，所以选A.
gap: rev的降幅大於成本的降幅
A：revenue decrease>cost decrease
因为收入的降幅大于成本的降幅。
A：FD的额外收入比SD的额外支出要高。---如果发生了change，额外收入下降，那么利润也下降