90 and 70. If the respective credits received for these courses are 3, 5, 3 and 2, determine an appropriate average grade. (3 marks) Question Four (15 Marks) (i) A parking building which is open for 7 hours a day has the following fee policy: 18 dollars per hour for the first 3 hours of parking and 6 dollars for each additional hour. Many years of data shows that the number of hours of parking for a car, denoted X, is a discrete random variable with probability function sok - K 8 -k for k = 1, 2, ... , 7 128 P(X = 1) = otherwise. What is the mean parking charge for a car in dollars under this policy? What is the corre- sponding standard deviation? discrete p(x=x) = 8-K for K= 1, 2/3--7 marks) mean parking charge : E CO) = = 20 4 60) = 2 K(8-1 (51 E kgov 128 28 Page 2 of 3