Use the two steps for solving a linear programming problem, given in the box on page 606, to solve the problems in Exercises 17–23.

Food and clothing are shipped to survivors of a natural disaster. Each carton of food will feed 12 people, while each carton of clothing will help 5 people. Each 20-cubic-foot box of food weighs 50 pounds and each 10-cubic-foot box of clothing weighs 20 pounds. The commercial carriers transporting food and clothing are bound by the following constraints:
• The total weight per carrier cannot exceed 19,000 pounds.
• The total volume must be less than 8000 cubic feet. How many cartons of food and clothing should be sent with each plane shipment to maximize the number of people who can be helped?