3. A box contains two fair coins and two biased coins (each with P ("heads") = 0.3). A coin is chosen at random from the box and tossed four times. Suppose two heads and two tails are obtained. (7) (a) Find the posterior probability that the chosen coin is fair. (5.5) 8.5 5((5-2) (1.3)) (6) (b) Find the posterior probability that the chosen coin is biased. 72.3.5 (5.5²+5)+5(-74.3²)) 1.29 14137 5863463