Consider a pair of discrete random variables (X1, X2) with pmf given below. The range of X1 is {1, 2, 4, 6} and that of X2 is {3, 8}. Round answers to 4 decimal places. Part a] What is the pmf of the distribution of X2 conditional on X1 = 4 evaluated at 332 = 8 (in symbols: f2|1(8|4) = P(X2 = Sle = 4))? Part b] What is the value of E(_X2|X1 = 4)