A Medical Equipment Testing and Calibration Service Is Depicted in Figure

A medical equipment testing and calibration service is depicted in Figure 1. 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 a billing clerk prepares the invoice (step 5) simultaneously, and the customer is contacted by phone for pick-up (step 6) . The average throughput is 3 equipment units per hour. Figure 1 Flow chart of the medical equipment testing and calibration service process
The table below shows the work content of the process steps, activity times in minutes per unit, shared and non-shared work activities, and the type of resource required. There are 3 service technicians on duty: 1 inspector, 1 billing clerk, and 1 shipping clerk.
$$\begin{array} { | c | c | c | } \hline \text { Activity } & \begin{array} { c } \text { Activity } \\\text { Time } \\\text { (minutes) }\end{array} & \text { Activity Performed By } \\\hline \text { Start } & - - & \\\hline 1 & 8 & \text { Service technician } \\\hline 2 & 17 & \text { Service technician } \\\hline 3 & 25 & \text { Service technician } \\\hline 4 & 12 & \text { Inspector } \\\hline 5 & 3 & \text { Billing clerk } \\\hline 6 & 7 & \text { Billing clerk } \\\hline 7 & 25 & \text { Shipping clerk } \\\hline \text { End } & - - & \\\hline\end{array}$$
-The labor utilization rate (%) for the billing clerk is _____.

A) 25%
B) 50%
C) 75%
D) 100%