A company knows that the product demand for the next 4 semesters is as follows: semester 1 is X1 units, semester 2 is X2 units, semester 3 is X3 units, and semester 4 is X4 units.

To meet this demand, the company wants to create a production schedule at the beginning semester. During each semester, if a product is produced, it will incur a machine set-up fee of IDR Y1 and a variable fee of IDR Y2 per unit. At the end of each semester, if a product is stored, it will incur a saving cost of IDR Y3 per unit. Production capacity and storage capacity are M1 and M2, respectively. Create a recursion equation that can be used to determine the company's production schedule.