A company must determine which of 8 products (x_1, x_2, x_8) to discount. The goal is to maximize the additional exposure gained from the discount. The respective additional exposure levels for the 8 products are (15, 10, 5, 2, 25, 13, 5, 4), At least two and no more than five products may be discounted. Additionally, x_1 and x_2 cannot both be discounted, an at least one at can be solved to give the optimal set of products to be discounted. Formulate a mathematical programming problem that can be solved to give the optimal set of products to be discounted.