Answer:
The answer is 8.
Step-by-step explanation:
He is guaranteed to make $240 between 2 and 6 pm every Saturday afternoon. For each time that both of the 2 customers booked for the same hour does not cancel, he earns only $20. Considering that the probability of cancellation is 25%, if he books 8 customers for the 4 hour period on Saturday afternoon, he is making an extra $80 which bumps up his total earnings to $320. If he accepts any booking after 8, each is going to cost him $40. So the total number of reservations he should take is 8.
I hope this answer helps.