4. Given independent random variables with means and standard deviations as shown, find the mean and standard deviations of these combinations of the variables: HINT: See Lecture 15,pp.3-4: Standard deviation, 6, cannot be added/subtracted, but Variance can. Remember var(x) = 033 Mean SD Var 5. Based on past experience a delivery company's trucks will average 1.3 parking tickets per truck per month, with a standard deviation of 0.7 tickets. a) If they have 18 trucks, what are the mean and standard deviation of the total number of parking tickets the company will have to pay this month