Refer to Exercises 5.7, 5.25, and 5.51. Let Y1 and Y2 have joint density function f (y1, y2) = e−(y1+y2) , y1 > 0, y2 > 0 0, elsewhere. 262 Chapter 5 Multivariate Probability Distributions a What are E(Y1 + Y2) and V(Y1 + Y2)? b What is P(Y1 − Y2 > 3)? c What is P(Y1 − Y2 < −3)? d What are E(Y1 − Y2) and V(Y1 − Y2)? e What do you notice about V(Y1 + Y2) and V(Y1 − Y2)?