Maria and Jonathon were selling shirts at a flea market for $13 per shirt. However, they had the ability to bargain with purchasers down to a minimum price of $10. At the end of the day, they had sold 2 shirts for $10, 3 shirts for $12, 2 shirts for $12.50, and 5 shirts for $13. To the nearest cent, what was their mean price?