The length of time, in minutes, for an airplane to obtain clearance for takeoff is a random variable Y = 4X + 2, where X has the density function: f(x) = 1/3 e^(-x/3) for x > 0 Find the variance of Y. ----- I found the expected value of X to be 14 minutes, which was correct. This means the variance for X will be: E(X^2) - E(X) = 18 - 14 = 4. Will the following work for the variance? Var(Y) = (4^2)(4) = 64. If so, what does that mean to have a "negative" take off time? Thanks for your help!! :)