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An Auto Body Shop has five cars waiting for Economy Detailing. An Economy Detailing consists of a wash and then a hand wax. Cars cannot be waxed until they are washed.
| Wash (Hours) | Wax (Hours) | |
| Jaguar | 3 | 3 |
| Cadillac | 5 | 2 |
| Ford | 1 | 1 |
| Honda | 2 | 1 |
| Lexus | 4 | 3 |
a. What schedule produces the shortest time span in which these orders can be completed?
b. How many hours does it take to complete the five orders?
c. For the schedule in question a, how many hours is the waxing task idle?
d. When will Dave finish the Cadillac?
e. What is the average order completion time?
Expert Answer
a) Schedule that produces the shortest time span is determined using Johnson’s rule as follows.
The Shortest time span schedule is Ford, Jaguar, Lexus, Cadillac, Honda
b) 16 hours
c) Waxing idle time = 16 – (1+3+3+2+1) = 6 hours
d) at 15 hours
e) Average completion time = (2+7+11+15+16) / 5 = 10.2 hours
