Consider a four-step serial process with processing times given in the list below. There is one machine at each step of the process and this is a machine-paced process.

Step 1: 26 minutes per unit
Step 2: 16 minutes per unit
Step 3: 23 minutes per unit
Step 4: 26 minutes per unit

Assuming that the process starts out empty, how long will it take (in hours) to complete a batch of 91 units?