ANSWER
The mean value of the population is 105
Explanation:
According to the question, we were given the following parameters
Given parameters:
Random sample = 21 employees
standard deviation = 5.7 hours
Confidence interval = 99%
Mean=?
The mean can be calculated using the below formula

The z- score for 99% confidence interval = 2.576
The next thing is to substitute the above parameters into the formula

Hence, the mean value of the population is 105