A computer lab has three laser printers and five toner cartridges. Each machine requires one toner cartridges which lasts for an exponentially distributed amount of time with mean 6 days. When a toner cartridge is empty it is sent to a repairman who takes an exponential amount of time with mean 1 day to refill it. (a) Compute the stationary distribution. (b) How often are all three printers working