An airline with two types of airplanes, P1 and P2, has contracted with a tour group to provide transportation for a minimum of 2000 first-class, 1500 tourist-class, and 2400 economy-class passengers. For a certain trip, airplane P1 costs $12 thousand to operate and can accommodate 40 first-class, 40 tourist class, and 120 economy-class passengers, whereas airplane P2 costs $10 thousand to operate and can accommodate 80 first-class, 30 tourist-class, and 40 economy-class passengers. How many of each type of airplane should be used in order to minimize the operating cost?