THE ANSWER IS 20, BUT I NEED TO PROVE WHY

Listed below is the minimum amount of nurses that need to be staffed per day of the week at a hospital:

Monday - at least 5 nurses working

Tuesday - at least 13 nurses working

Wednesday - at least 15 nurses working

Thursday - at least 19 nurses working

Friday - at least 14 nurses working

Saturday - at least 16 nurses working

Sunday - at least 11 nurses working

Each nurse may start on any day of the week, but must work 5 consecutive days with 2 consecutive days off.

Use Excel to prove the minimum number of nurses that can be hired to meet shift requirements and follow the 5 days on and 2 days off set schedule. (Hint: Some days will have more nurses than the shift requires).

Please show proof formulas in Excel!!