4. During a typical Pennsylvania winter, I-80 averages 1.7 potholes per 10 miles. A certain county is responsible for repairing potholes in a 30-miles stretch of the interstate. a) Find the probability that the number of potholes the county will have to repair is between 5 and 10 (both inclusive) next winter. b) The cost of repairing a pothole is $5000. Find the mean and variance of the county's pothole repair expense for next winter.