My linear programming problem

You are the owner of a small cupcake store, the mathematical cupcake shop, and you make two kinds of cupcakes, soft vanilla and crunchy vanilla.  Baking a set of soft cupcakes takes 3 cups of cupcake mix and 6 cups of milk.  While baking a set of crunchy cupcakes uses 3 cups of cupcake mix and 3 cups of milk.  In stock you have about 20 cups of cupcake mix and 18 cups of milk.  You normally make $6 per set of soft cupcakes and $4 per set of crunchy cupcakes.  How many sets of each type of cupcake should you make to get the most profit?