Refer to the figure below. Green will first be processed on machine 2 for 1 hour, then on machine 1 for 2 hours, and finally on machine 3 for 1 hour. Green is due at the end of hours 8. Red and Blue are fixed, you may not move them. Using Backward scheduling:

options:

You will finish Green in hour 7

No feasible schedule is possible.

You will start Green on Machine 2 in hour 5

You will start Green on Machine 2 in hour 1

Hour Machine 1 Machine 2 Machine 3 RED BLUE RED BLUE BLUE BLUE BLUE RED RED