9) The Acme Class Ring Company designs and sells two types of rings: the VIP and the SST. They can produce up to 24 rings each day using up to 60 total man-hours of labor. It takes 3 man-hours to make one VIP ring and 2 man-hours to make one SST ring. How many of each type of ring should be made daily to maximize the company's profit, if the profit on a VIP ring is $40 and on an SST ring is $30?

10) Zach is planning to invest up to $45,000 in corporate and municipal bonds. The least he will invest in corporate bonds is $9000 and he does not want to invest more than $28,000 in corporate bonds. He also does not want to invest more than $26,084 in municipal bonds. The interest is 8.4% on corporate bonds and 6.2% on municipal bonds. This is simple interest for one year. What is the maximum value of his investment after one year? 11) A company makes two kinds of engineering pencils, Type I and Type II (deluxe). Type I needs 2 min of sanding and 6 min of polishing. Type II needs 5 min of sanding and 3 min of polishing. The sander can run no more than 66 hours per week and the polisher can run no more than 73 hours a week. A $3 profit is made on Type I and $5 profit on Type II. How many of each type should be made to maximize profits?

12) An airline with two types of airplanes, P1 and P2, has contracted with a tour group to provide transportation for a minimum of 400 first class, 750 tourist class, and 1500 economy class passengers. For a certain trip, airplane P1 costs $10,000 to operate and can accommodate 20 first class, 50 tourist class, and 110 economy class passengers. Airplane P2 costs $8500 to operate and can accommodate 18 first class, 30 tourist class, and 44 economy class passengers. How many of each type of airplane should be used in order to minimize the operating cost?

13) A summer camp wants to hire counselors and aides to fill its staffing needs at minimum cost. The average monthly salary of a counselor is $2400 and the average monthly salary of an aide is $1100. The camp can accommodate up to 35 staff members and needs at least 20 to run properly. They must have at least 10 aides, and may have up to 3 aides for every 2 counselors. How many counselors and how many aides should the camp hire to minimize cost?