In a single phase single server service process where both interarrival time and service times are exponentially distributed, it can be assumed that the total time that a customer spends in the process is also exponentially distributed. Suppose the total time the customers spend in a pharmacy is exponentially distributed with mean of 6 minutes. The pharmacy has promised to fill all prescriptions in 16 minutes.

1. What percentage of the customers cannot be served within this time limit?

The potential answers are:

A: 9.7%

B: 8.21%

C: 4.98%

D: 13.53%

E: 6.95%

2. 86% of customers are served in less than what time interval?

The potential answers are:

A: 4.98 minutes.

B: 3.22 minutes.

C: 4.24 minutes.

D: 11.8 minutes.

E: 6.36 minutes.

3. What is the probability of arrival of exactly 4 customers in 18 minutes.

The potential answers are:

A: 18.04%

B: 15.63%

C: 22.4%

D: 16.8%

E: 27.07%

4. What is the probability of arrival of at most 4 customers in 18 minutes.

The potential answers are:

A: 81.53%

B: 78.51%

C: 64.72%

D: 94.73%

E: 67.67%