part (a)

A device containing two key components fails when, and only when, both components fail. The lifetimes, T1and T2, of these components, are independent with common density functionf(t)=e^t, t > 0. The cost, X, of operating the device until failure is 2T1+ T2. Find P(X<2)

part (b) The profit for a new product is given by Z = 3X - Y - 5. X and Y are independent random variables with Var(X) = 1 and Var (Y) = 2. What is the standard deviation of Z?