S&S operates its large supermarkets19 on a 24-hour per day basis using only part-time cashiers working shifts of 2 to 5 hours per day. All shifts start on the hour. The required number rh of cashiers on duty at a given store is known for (24-

clock) hours h = 0,c, 23, and managers can also estimate the number of employees bl willing to work shifts of lengths l = 2,c, 5. They seek a shift schedule that meets requirements at minimum total cashier hours worked. Formulate an LP model of this shift scheduling problem using the decision variable 1h = 0,c, 23; l = 2,c, 52 xh, l ! number of cashiers starting an l-hour shift at hour h Neglect the fact that the numbers working each shift must physically be integers.