A medical equipment testing and calibration service is shown below. The customer usually brings the equipment to the service center. The service process requires service technicians to perform three process steps #1 to #3. Each technician is cross-trained so they can perform any of the three steps. The inspector does step #4 alone. After step #4, two parallel work activities are performed. That is, a shipping clerk packs the work (step #7), while simultaneously, a billing clerk prepares the invoice (step #5), and the customer is contacted by phone for pick-up (step #6). The average throughput is three equipment units per hour.

What job represents the bottleneck in this process.
The ______ job is the bottleneck.
Billing Clerk
Inspector
Service technician
Shipping clerk