X = wage
(a) `Z_1=(2.75-3.25)/0.6=-0.83333 `
So about `56.6%` of the workers have wages between `$2.75` and `$3.69` an hour.
You can see this portion illustrated in the standard normal curve below.
The normal curve with mean = 3.25 and standard deviation 0.60, showing the portion getting between $2.75 and $3.69.
(b) W = minimum wage of highest `5%`
`z = 1.645` (from table)
Solving gives: `x = 4.237`
So the minimum wage of the top `5%` of salaries is `$4.24`.
In the graph below, the yellow portion represents the 45% of the company's workers with salaries between the mean ($3.25) and $4.24. (This is 1.645 standard deviations from the mean.)
The light green shaded portion on the far right representats those in the top 5%.
The right-most portion represents those with salaries in the top 5%.