20. The random variable X, representing the number of items sold in a week, has the following probability distribution: X O 1 2 3 4 5 6 P(X = X) 0.10 0.20 0.40 0.15 0.05 0.05 0.05 a) By the fourth day of a particular week, 3 items have already sold. What is the probability that there will be less than a total of 5 items sold during that week? b) What is the probability that in a given week there will be at most 4 items sold