3. Each day, workers at an emergency department work two 6-hour shifts chosen from 12 A.M. to 6 A.M., 6 A.M. to l 2 P.M., 12 P.M. to 6 P.M., and 6 P.M. to 12 A.M. the following number of workers are needed during each shift: 12 A.M. to 6 A.M.- 20 workers; 6 A.M. to 12 P.M.- 7 workers; 12 P.M. to 6 P.M. -13 workers; 6 P.M. to 12 A.M.9 workers. Workers whose two shifts are consecutive are paid S10 per hour; workers whose two shifts are not consecutive are paid $20per hour. Formulate an LP that can be used to minimize the cost of meeting the daily emergency department requirement