A Company That Receives Most of Its Orders by Telephone

Multiple Choice

A company that receives most 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