prep的一题

At present the Hollywood Restaurant has only standard-height tables. However, many customers come to watch the celebrities who frequent the Hollywood, and they prefer tall tables with stools because such seating would affard a better view of the celebrities. Moreever, diners seated on stools typically do not stay as long as diners seatd at standard-height table. Therefore, if the Hollywood replaced some of its seating with high tables and stools, its profits would increase.

The argument is vulnerable to critism on the grounds that it gives reason to believe that it is likely that

A. a customer of the Hollywood who would choose to sit at a tall table would be an exception to teh generalization about lingering

B. a restaurant's customs who spend less time at their meals typically order less expensive meals than those who remain at their meals longer

Can someone explain the meaning of the question and why A is correct and B is not. Thanks