The school of business has 3 fax machines. The toner in each machine needs to be changed after about 5 hours of use. There is one unit secretary who is responsible for the fax machine maintenance. It takes him 15 minutes to replace the toner cartridge. Suppose that the probability the maintenance system is empty = 0.8578, what is the average number of fax machines in the queue? (rounding to 4 decimal places.) O 1.6666 O 2.0995 O 0.1568 O 0.0138 none of the above