A bakery bakes cheesecakes and Black Forest cakes. During any month, he can bake at most 70 cakes. The demand for cheesecakes is 45, 25 and 20 in months 1, 2 and 3. The demand for Black forest is 15, 25 and 15 in months 1, 2 and 3. The costs per cakes are $3, $3.4, $3.8 (for cheesecakes) and $2.5, $2.8 and $3.4 (for Black Forest cakes) in months 1, 2 and 3 respectively. It costs 40 cents to hold a cheesecake, and 50 cents to hold a Black Forest case, in inventory for a month. Identify the decision variables, objective function and relevant constraints for the above descriptions.