An online bookseller uses one of four shipping companies to send packages to its customers. Any package can be sent with one and only one of these companies. Denote the following events: C1: the package is shipped with company 1, C2: the package is shipped with company 2, C3: the package is shipped with company 3, C4: the package is shipped with company 4. The bookseller uses the shipping companies with the following probabilities: P(C1) = 0.5, P(C2) = 0.25, P(C3) = 0.125, P(C4) = 0.125. Let X be the event that the package arrives on time at its destination. Depending on the shipping company used, the probability of X varies: P(X|C1) = 0.85, P(X|C2) = 0.9, P(X|C3) = 0.8, P(X|C4) = 0.8.
5.1) Compute the numerical value of P(C2 U C3).
5.2) Given that a package has arrived on time, what is the probability that it was shipped with company C1?
5.3) Are the events C1' and X independent?
5.4) What is the probability that the package will not arrive on time exactly 3 times out of 10 times?