Answer:
(a)Mean: It increases by $23.
(b)Median: It stays the same.
Explanation:
The weekly salaries are given below:

Part A
First, we find the mean of the initial salaries:

If the $538 salary changes to $699, then:

The difference = 830-807=23.
Therefore, if the $538 salary changes to $699, the mean increases by $23.
Part B
The median is the item in the middle of the data.
The initial weekly salaries are:

If the $538 salary changes to $699, the new weekly salaries are:

The median stays the same.