A plant has a large number of similar machines breakdown/failure are random and independent. The shift in charge of a plant collected the data about various times, machine break down & repair time required on hourly basis & the data are tabulated.

First table is the time 4 machine break down & then probability

0.5                                                0.05

1                                                   0.06

1.5                                                0.16

2.0                                                0.33

2.5                                                 0.21

3                                                    0.19

Second table is

Repair time required                   Probability

1                                                      0.28

2                                                      0.52

3                                                       0.20

For each hour that a machine is down due to being repaired or waiting to be repaired, the plant loses 70 rupee a by way of cost production. A repair man is paid 20rupees per hour. Simulate this maintenance system for 15 breakdown & how many repair men should the plant hire for repair work?