A hotel has 115 guest rooms, assume the following length of time for cleaning the following room status

- 20 minutes for a vacant room

- 15- 30 minutes for occupied stay over room

- 45 -1 hour for a departure/ arrival room.

How many housekeepers are required if they work 10 hours a day 4 days a week with 3 OFF DAYS? How many rooms can a housekeeper service in a 10 hours shift?

Take into account off days and relief housekeepers to ensure that service continues. What is the total number of housekeepers that are required for the department? Please show all workings to understand better.