4. [cLO?] A Girl Scout troop sells cookies from house to house. Given that the probability of selling a set of cookie packs at any house they visit is 0.4 and it is assumed that they sell exactly one set to each house that buys their cookies. Calculate the following probabilities. (a) The probability that the house where they make their first sale is the fifth house they visit. [5 marks| (b) The probability that they sold exactly 6 sets of cookie packs, given that they visited 10 houses on a particular day. [5 marks] (c) The probability that on a particular day the third set of cookie packs is sold at the seventh house that the girls visit. [5 marks]