Final answer:
The average arrival rate of customers is 1 customer every 2 minutes. The average time it takes for three customers to arrive is 6 minutes.
Step-by-step explanation:
a. The average arrival rate of customers is 1 customer every 2 minutes. Therefore, on average, 2 minutes elapse between two successive arrivals.
b. The average time it takes for three customers to arrive is 6 minutes. This can be calculated by multiplying the average arrival rate (1 customer every 2 minutes) by the number of customers (3).