c) Suppose that X is a continuous random variable that represent the customers' waiting time (in minutes) after getting a queue number at post office. The probability density function is given as follows: f(x) = 1Sx54 24 elsewhere Show that s = 1. (3 marks) Find that the customer's waiting time after getting a queue number at post office is not less than 1.5 minutes. (3 marks) Ill) Calculate E(X ). (4 marks) lv) Find the standard deviation of X given that E(X) = 95 32 (2 marks) v) Find the total variance of X and Y. if the variance of Y is = (2 marks)