1. Quick Question Help - Probability

#1
Hi Guys,

Could I please get any insight into how to go about this:

Q. The hazard rate function for a component at time t is given by:
0.0006 per hour if t ≤ 5 hours
0.0015 per hour if t > 5 hours and ≤ 50 hours
0.0042 per hour if t > 50 hours
What is the reliability of this component at 75 hours?

The way I have worked it out is like this:
A.
1-0.0006 = 0.9994
1-0.0015 = 0.9985
1-0.0042 = 0.9958

So the reliability at 75 hours it would be:
(0.9994^5) * (0.9985^45) * (0.9965^25) = 0.916078

,thoughts???

Thank you!