Respuesta :
The revenue in the problem is equal to $400 that is to be made out of 100 books selling at $8 each. The minimum number of books he has to seel is $400/$8 per book of 50 books. The maximum number is 100 books. Hence the answer to this problem is 50 ≤ x ≤ 100.
The answer would have to be D because 50 times 8 equals exactly 400. so the x would have to be greater than or equal to 50, but less than or equal to 100 because he can only sell a maximum of 100 books.