The System consists of $3$ computing nodes and $1$

decision node $($voter$).$ All nodes fails and repairs

according to Poisson process

Computing node fails with frequency $[\frac{1}{h}]$ and its average time

to repair is $\frac{1}{}[h]$

Voter fails with frequency $v[\frac{1}{h}]$ and its average time to repair is

$\frac{1}{}[h]$

When voter fails it means that whole system fails $($when

voter repairs all other nodes repair$).$ The system is in

operational state when at least two computing nodes

and voter works.

What is the probability that the system is in operational

state?