You manage a 24–hour store where workers can come in at the beginning of any 4 hour interval, starting at midnight, and work an 8-hour shift. Based on store activity levels, the numbers of employees needed during the different 4-hour intervals in the day are given below. Time range 12:00 – 4:00 AM 4:00 – 8:00 AM 8:00 – 12:00 Noon 12:00 – 4:00 PM 4:00 – 8:00 PM 8:00 – 12:00 Midnight # Employees Needed 6 9 12 10 18 14 How many decision variables are needed to formulate this problem?