(a) [10 pts] Suppose 11,242, .43 are events such that P(A1 HA2} = P(A1 HA3} 75 0 while P(A2 I\"! A3) = 0. Calculate the probability that at least one of these events occurs by calculating P(A1 U A2 U A3} in terms of only P(A1), P(Ag), P[A3) and P(A1 ['1 A2). [b] [5 pts] If A1, 442,143 are pairwise independent events is it possible that P(A1 r1 A2} = P(A1 Pl A3} 75 0 while P(A2 A3) = D, and what does it sag.r about the events 11,142, A3? You have to justify your answer with a calculation