Suppose the firm has signed a contract to purchase 70 ounces of rubber. This contract must be honored. Furthermore, the rubber has a very short shelf life if not used for production. That is, if the rubber is not used immediately, it will be wasted. Let 1 be the price of an ounce of rubber, and 2 be the price of an ounce of plastic. Suppose the firm wants to make 170 cell phone cases. The conditional factor demand for ounces of plastic totals if 12 2, and zero otherwise