In: Other
Solution :
The rate of system is defined by machine with largest time per unit i.e. bottleneck resource.
In this case, biottleneck is Step : 3 with time 30 min per unit.
So system requires 30 * 105 min = 30 * 105 / 60 hours = 52.5 hours at bottleneck.
time for first unit at Step 1 and 2 and for last unit at step 4 is - 25 + 15 + 20 - 60min - 1 hr.
So total time for system is 52.5 + 1 - 53.5 hours.