an airline with two types of airplanes, x and y, has contracted with a tour group to provide accommodation for a minimum of each of 2800 first-class, 2000 tourist, and 5600 economy-class passengers. airplane x costs $15000 to operate and can accommodate 40 first-class, 40 tourist, and 20 economy-class passengers, while airplane y costs $12000 to operate and can accommodate 20 first-class, 10 tourist, and 70 economy-class passengers. if the goal is to find the number of each type to minimize operating costs, write the objective function and all constraints for this linear programming problem. note: you just need to set up lp, so do not solve.