The time between accidents in a day in town A is given by T and the time between accidents in a day in town B is given by S. The joint density function for T and S is f(t,s)=e^ -(t+s) , for t≥0 and s≥0.
(a) Calculate the expected value of T.
(b) Calculate the expected value of S
(c) Calculate the expected value of 2T+3S.