The Red Rock School District has six buses in its fleet. The time between bus failures follows an exponential distribution with a mean of twenty days. During the time a bus is out of commission, the district must lease another bus at a cost of $80 per day.The district is considering hiring Tom to handle maintenance. It is estimated that Tom can repair a bus in an average of 10 hours, and Tom wants a salary equivalent to $160 per working day. A working day lasts 8 hours, and there are 200 working days per year. What is the daily cost if Tom is hired? 

a. 165.33

b. 182.40

c. 197.86

d. 540.12

e. None of the above