John had a collection of comic books. He decided to sell some over four weeks. In the first week, he sold of his comic books plus 5 books. In the second week, he sold of the remaining comic books plus 2 books. In the third week, he sold of the remaining comic books plus 6 books. In the fourth week, he sold of the remaining comic books plus 4 books. After the fourth week, he had 20 comic books left. How many comic books did John have initially?
150
155
160
165
170
