[20 points] Dans Auto Detailing business performs two major activities: exterior cleanup, and interior detailing. Based on the size of car and condition, time estimates for six cars on Monday morning are as shown in the accompanying table.

Car Number 1 2 3 4 5 6

Exterior 50 35 90 65 45 80 Interior 30 40 20 45 25 55

a. Sequence the cars so that all exterior detailing is done first and total completion time is minimized. (Hint: This is a two-facility problem) b. Draw a Gantt chart and evaluate the idle time.