A launderette has 10 washing machines which are in constant use. The times between two successive failures of a washing machine have an exponential distribution with mean value 100 hours. There are...

A launderette has 10 washing machines which are in constant use. The times between two successive failures of a washing machine have an exponential distribution with mean value 100 hours. There are two mechanics who repair failed machines. A defective machine is repaired by only one mechanic. During this time, the second mechanic is busy repairing another failed machine, if there is any, or this mechanic is idle. All repair times have an exponential distribution with mean value 4 hours. All random variables involved are independent. Consider the steady state.

1) What is the average percentage of operating machines?

2) What is the average percentage of idle mechanics?