This is a queue model of MM 1. The arrival of customers obeys Poisson distribution with parameter 4, and the service time obeys negative exponential distribution with parameter 60/ 10 = 6, so p=4/6=2/3, that is, the probability that the system is busy is 2/3.

1, and the probability of idle time is 1-2/3 = 1/3.

2. The average number of customers in the store LS = 4/(6-4) = 2.

3. Residence time WS = 1/(6-4) = 0.5 hours.

4. The waiting time is 2/3/(6-4) = 1/3 hours.

The hairdressing time is 0.5- 1/3 = 1/6 hours.