新东方的黄皮书section54的第4题和17题。
4题:if the shelf space for bakeries A and B were reversed and their average weekly sales per foot remained the same,then the total average weekly sales would do which the following?
(Bakery A:average weekly sales $1100;shelf space 25ft;average weekly sales per foot of shelf space $44)
(Bakery B:average weekly sales $500;shelf space 20ft;average weekly sales per foot of shelf space $25)
A:Decrease by $220
B:D by $95
C:Remain unchanged
D:Increase by $125
E:I by $345
答案:B