First, let's calculate the minutes that each tour guide works in a day.
They lead ten 45 minute tours each day. Thereby,
Each tour guide works 450 minutes per day
This means that, in total, 900 person-minutes are needed every day.
Now, let's convert this to hours using a rule of three:
This way,
The number of person- hours per day for the tours is 15 (Ans: A)