A single server queuing system with a Poisson arrival rate and exponential service time has an average arrival rate of 13 customers per hour and an average service rate of 18 customers per hour. The probability of 3 customers in the system is : O a. 0.8954 O b. 0.1046 O c. 0.2778 O d. 0.6233 Determine which delivery alternative would be most economical for 80 boxes of parts. Each box costs $365 and the annual holding cost is 30% of the cost. Assume 365 days per year. Alternatives Freight cost for all 80 boxes Overnight $300 Eight-day $132 Select one: O a. The eight-day option is at least $20 cheaper than overnight O b. Both options are equally economical Oc. All the choices are incorrect O d. Overnight option is at least $20 cheaper than eight-day