7. Baking a tray of chocolate chip cookies takes three cups of milk and two cups of flour. Baking a tray of oatmeal raisin cookies takes one cup of milk and four cups of flour. The baker has 9 cups of milk and 16 cups of flour available. He makes $2.50 profit per tray of chocolate chip cookies and $2 profit per tray of oatmeal raisin. How many trays of each type of cookies should be make to maximize his profit?