Im still having trouble with fraction and decimals pls

Hello i need some with trigonometric substitutions. [tex]\int\limits^a_b {x} \, dx[/tex]

I’m on question 7 it says a covered water tank is in the shape of a cylinder the tank has a 28 inch diameter and a height of 66 inches to the nearest square inch what is the surface area of the water tank

How can you find the mean absolute deviation (mad) for this set of data?