Slate Truck Company manufactures trucks and identifies each truck with a unique serial plate. On December 31, a customer ordered 5 trucks from the company, which currently has 20 trucks in its inventory. Ten of these trucks cost \(\$ 20,000\) each, and the other 10 cost \(\$ 25,000\) each. If Slate wished to minimize its net income, which trucks would it ship? By how much could Slate reduce net income by selecting units from one group versus the other group?