Katie Posh runs an upscale nail salon. The service process includes five activities that are conducted in the sequence described below. (The time required for each activity is shown in parentheses):
Three servers (S1, S2, and S3) offer the services in a worker-paced line. The assignment of tasks to servers is the following: S1 does Activity 1. S2 does Activities 2 and 3. S3 does Activities 4 and 5. The drying process does not require server 3?s constant attention; she/he needs to only escort the customer to the salon?s drying chair (equipped with fans for drying). The time to do this is negligible. There exists only one drying chair in the salon.
Which resource is the bottleneck of the process?