You and your classmates had a school project to go to an amusement park for a day. For that, every student had to complete a task to get money. You were assigned to bake cookies and sell them. Today, it was a rainy day, but you decided to sell cookies anyway. Of course, you put them in a box to prevent them from getting wet. You were waiting for someone to come, in a corner with a bench. Suddenly, you hear a klaxon, when you look up, it’s a police car. Immediately, you start panicking. As the officer pulls down the window, he asks " How much are the cookies? " you were confused but remembered that you had written down ' selling cookies ' on your box. You responded " 2$ a cookie, 5$ the set of 4 cookies. " He nodded and parked his car as he approached you with his wallet.