Consider the following game. There is a bottle with 20 colored chips inside. There are 2 blue chips, 4 purple chips, 7 green chips, and 7 red chips. You pay $2 and pick one out at random. If you pick a blue chip, you get a prize of $10. If you pick a purple chip, you get a prize of $5. You get nothing for red or green chips. What is the expected value of playing the game?