7. [15 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 123456 Exterior 35 20 40 30 25 45 Interior 24 32 26 42 36 28 a. Sequence the cars so that all exterior detailing is done first and total completion time is minimized. What is the sequence? (Hint: This is a two-resource problem) b. Draw a Gantt chart and evaluate the idle time for each activity. What is the total idle time