Multi period Employee Scheduling Problems explanation

Volunteers work for your non-profit for 2 weeks at a stretch in the summer. The total time span is 6 weeks where you need volunteers. You need 10 in week 1, 7 in week 2, 8 in week 3, 12 in week 4, 7 in week 5 and 7 in week 6. Those who begin work in any of the first 5 weeks continue to work for 2 weeks from the time they begin. However, those you begin in week 6 only work for that week, and then your summer project is done. How would you minimize the number of volunteers needed to satisfy the requirements? 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. What is the minimum number of employees you would need on your payroll overall to meet or exceed the requirements?