4. Two foods, A and B contain the number of units of protein and starch per kg as shown in the table. Units of protein Units of starch Cost per kg A 4 5 $4 B 6 3 $5 Minimum daily 16 11 If the daily intake from these two foods is to be at least 16 units of protein and 11 units of starch, what is the cheapest way of satisfying the conditions? 5. The Century Corporation produces two lines of products, washing machines and refrigerators. Each washing machine takes 6 hours of wiring and 2 hours of drilling. Each refrigerator takes 10 hours of wiring and 5 hours of drilling. At the moment, 300 hours of wiring time and 150 hours of drilling time are available. Each washing machine yields a $100 profit, and each refrigerator yields a $120 profit. What combination of washing machines and refrigerators is optimal? 6. This company produces two products: bed mattresses and box springs. A prior contract requires that the firm produce at least 30 mattresses or box springs, in any combination per week. In addition, union labor agreements demand that stitching machines be kept running at least 40 hours per week, which is one production period. Each box spring takes 2 hours of stitching time, and each mattress takes one hour on the machine. Each mattress costs $20, each box spring costs $24. Formulate this problem to minimize total production costs and solve graphically.