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 5 minutes. The pharmacy has promised to fill all prescriptions in 11 minutes.

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

The potential answers are:

A: 11.08%

B: 13.53%

C: 9.07%

D: 5.88%

E: 6.08%

2. 83% of customers are served in less than what time interval?

The potential answers are:

A: 9.83 minutes.

B: 8.86 minutes.

C: 4.83 minutes.

D: 7.33 minutes.

E: 6.64 minutes.

3. What is the probability of arrival of exactly 5 customers in 20 minutes.

The potential answers are:

A: 15.63%

B: 19.54%

C: 16.8%

D: 18.04%

E: 22.4%

4. What is the probability of arrival of at most 5 customers in 20 minutes.

The potential answers are:

A: 78.51%

B: 98.34%

C: 62.88%

D: 91.61%

E: 43.35%