Answer:
Total number of employees at Tia's toy store

Explanation:
To find the number of employees who worked on Tia's store .
We have to add the total number of values from the employee column.
As the question mentioned.
Each of the staff members have different number of hours of sleep on thanksgiving night.
So
The summation of the number of employees from the frequency table

So there are
employees working on thanksgiving night in Tia's store.