Pieces of 2 by 4 by 72 lumber sold by a certain yard have been observed by a consumer watchdog to have 0, 1, 2, 3, 4, or 5 visible flaws (but rarely more). The probabilities for various numbers of flaws are provided by its cumulative distribution function Fr)Px: 0 4 Fox) .45 .67 .81 .89 96 a) As a customer, I find it unacceptable to buy such a piece of lumber if it has more than 3 flaws. What is the probability that a piece I buy will by accident be unacceptable? b) Find the average number of flaws in a piece of lumber chosen arbitrarily, E(X)