请教猴哥112数学难题第89题（具体见内）

b3gUID：2292411

Rack A holds 80 pairs of slacks with prices ranging from $12 to $15 a pair, and rack B holds 60 pairs of slacks with prices ranging from $13 to $18 a pair. If all the slacks are sold, what is the greatest amount by which the revenue from the sale of slacks on rack A could possibly exceed the revenue from the sale of slacks on rack B?

A $430
B $412
C $122
D $120
E $112

答案是B。但是我计算出来为什么是420呢？12*80 - 13*60 = 420。应该怎样做此题？

谢谢大家 8-)

caoyangbjfuUID：2274016

:) , 极端情况就是,RANGE A 一双13,其余15, RANGE B 一双18, 其余13
记住看清RANGE FROM
15*79+12-13*59-18=412

aefiterUID：2134740

15*79+12-59*13-18

b3gUID：2292411

谢谢大家。原来这题有这么大一个陷阱。

ＳＰесιalUID：3590654

前辈，求问陷阱是什么？range from A to B 我以为就是取值范围的意思，难道还有什么深意？求教为何不是420！