formulate please not solve

I want the objective and the decision variables and constraints

Each day, workers at the Gotham City Police Department work two 6-hour shifts chosen from 12 A.M. to 6 A.M., 6 A.M. to 12 P.M., 12 P.M. to 6 P.M.,and 6 P.M. to 12 A.M. The following number of workers is needed during each shift. Workers whose two shifts are consecutive are paid $12 per hour; workers whose shifts are not consecutive are paid $18 per hour. Formulate an LP that can be used to minimize the cost of meeting the daily workforce demands of the Gotham City Police Department. (HINT: Think of all possible combinations of shifts). Shifts Required workers 12 AM to 6 A.M. 15 workers 6 A.M. to 12 PM 5 workers 12 P.M to 6 PM 12 workers 6 P.M. to 12 A.M 6 workers