Scott and Ian design a cool T- shirt for snow boarders. Their friends are very impressed and everyone wants one. So, Scott and Ian set up a T-shirt printing business in their garage. The start up costs are $750 due to the availability of a used graphics machine. They estimate that it costs them $6.50 to print each T-shirt. They sell each T-shirt for $10.
Write an average profit per shirt function for producting x amount of shirts.