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? round to five decimal places.