A baker has 16 cups of milk and 15 cups of wheat flour on hand. He uses both milk and wheat flour when he makes com muffins and bran muffins. A tray of corn muffins requires 4 cups of milk, while a tray of bran muffins takes 2 cups of milk. A tray of com muffins requires 3 cups of wheat flour, and a tray of bran muffins also requires 3 cups of wheat flour. Let x equal the number of trays of corn muffins he can make, and let y equal the number of trays of bran muffins he can make.​