(no break for lunch? Where's the union steward?)
117 workers times 7.5 hours divided by 12 hrs per car means that 73.1 cars can be produced this shift.
Target 100 cars:
100 cars times 12 hrs per car means 1200 labor hours.
1200 hours divided by 117 workers is a 10.25 hour shift.
Add 10.25 hours to the start time will give the end of shift time.