GMAT Quantitative Reasoning Practice Test 5

Each of 20 people bought at least 1 book during a recent book sale. Among these people, 1 person bought exactly 3 books; each of 6 people bought fewer than 4 books; each of 3 people bought more than 7 books; and each of 2 people bought more than 10 books. How many people bought between 4 and 7 books, inclusive?