A Company That Receives the Majority of Its Orders by Telephone

Multiple Choice

A company that receives the majority of its orders by telephone conducted a study to determine how long customers were willing to wait on hold before ordering a product. The length of waiting
Time was found to be a variable best approximated by an exponential distribution with a mean
Length of waiting time equal to 3 minutes (i.e. the mean number of calls answered in a minute is
1/3) . Find the waiting time at which only 10% of the customers will continue to hold.

A) 2.3 minutes
B) 3.3 minutes
C) 6.9 minutes
D) 13.8 minutes