A Catalogue Company That Receives the Majority of Its Orders

Multiple Choice

A catalogue 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 time was found to be a random variable best approximated by an exponential distribution with a mean equal to 3 minutes.
-Find the waiting time at which only 10% of the customers will continue to hold.

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