The average wage of plumbers is normally distributed with a mean of $20 and a standard deviation of $5.50. (b) The ratio of plumbers earning between $18 and $22. (c) The ratio of plumbers earning more...

The average wage of plumbers is normally distributed with a mean of $20 and a standard deviation of $5.50.

 (b) The ratio of plumbers earning between $18 and $22.

 (c) The ratio of plumbers earning more than $28.

(d) The ration of plumbers earning less than $15.

 (e)  Compute the 70th Percentile.