Consider a four-step serial process with the number of workers at each step and processing times given in the following table. Process Step Number of Workers Time per Customer (in Minutes) 1 1 5 5 2 3 3 15 10 3 4 1 Assuming that the process starts out empty and is worker-paced, how long will it take (in minutes) to serve 20 customers? minutes to serve 20 customers