The length of time, in minutes, for and airplane to obtain clearance for take off at a certain airport is a random variable Y=3X-2, where x has the density function

f(x) = { 1/4e^(-x/4), x>0

0, elsewhere,

Find the mean and variance of the random variable Y.

the answer from the text book are: mean of Y = 10, variance = 144;

anyone know how to get the answers?