lIe I ll ll There are two trafc lights on a commuter's route to and from work Let X1 be the number of lights at which the commuter must stop on his way to work, and X2 be the number of lights at which he must stop when returning from work Suppose that these two variables are independent, each with the prnf given in the accompanying table (so X1, X2 is a random sample of size n = 2). p(x1) 0.4 0.3 0.3 ,4 = 0.9, a2 = 0.69 (a) Determine the pmf of To = X1 + X2. t a l o 1 2 3 4 p(t)\"0.16 V 0.24 / 0,33 / 0.15 / 009 / (b) Calculate \"T . a \"r = 1.3 / How does it relate to u, the population mean? I470=2 / 'M (c) Calculate a7 2. a a 2=l1.33 / a How does it relate to 02, the population variance?