X = wage

(a) `Z_1=(2.75-3.25)/0.6=-0.83333 `

`Z_2=(3.69-3.25)/0.6=0.73333`

So

`P(2.75<X<3.69)`

`=P(-0.833<Z<0.733)`

`=0.298+0.268`

`=0.566`

So about `56.6%` of the workers have wages between `$2.75` and `$3.69` an hour.

(b) W = minimum wage of highest `5%`

`x = 1.645` (from table)

`(x-3.25)/0.6=1.645`

Solving gives: `x = 4.237`

So the minimum wage of the top `5%` of salaries is `$4.24`.