Burning Brownie has five varieties of cakes as Chocolate fudge cake (Cake 1), Nutella-filled Cake
(Cake 2), Marble Cake (Cake 3), Cheese cake (Cake 4) and Fruit Cake (Cake 5) at their store. The
selling prices of each of the cakes are $9, $12, $4, $5, $8 respectively.
a. Formulate the Revenue function