(1 point) When parking a car in a downtown parking lot, drivers pay according to the number of hours they park. Let X denote the number of hours cars are parked. The probability distribution of X has been estimated as follows: X 2 3 4 5 6 7 8 P(X = x) 0.216 0.129 0.126 0.091 0.051 0.035 0.04 0.312 a) MX = b) ox = The cost of parking is 2.25 dollars per hour. Calculate the mean and standard deviation of the amount of revenue, R, each car generates. C) HR = d) OR =