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) . What proportion of customers having to hold more than 4.5 minutes will hang up before
Placing an order?

A) 0.22313
B) 0.48658
C) 0.51342
D) 0.77687