A school has 3 fax machines. The toner in each machine needs to be changed after about five (5) hours of use.?

A school has 3 fax machines. The toner in each machine needs to be changed after about five (5) hours of use. There is one secretary who is responsible for the fax machine maintenance. It takes him 15 minutes to replace the toner cartridge. What is the probability that two (2) fax machines need toner at the... show more A school has 3 fax machines. The toner in each machine needs to be changed after about five (5) hours of use. There is one secretary who is responsible for the fax machine maintenance. It takes him 15 minutes to replace the toner cartridge. What is the probability that two (2) fax machines need toner at the same time?
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