Assume that a two independent and identical unit parallel system, used in a transportation system, can fail either due to critical human errors or when all its units fail due to hardware failures or non-critical human errors. The constant hardware failure, critical human error, and noncritical human error rates are 0.0009 failures/ hour, 0.0001 errors/hour, and 0.0003 errors/hour, respectively .Calculate the system reliability for a 100-hour mission and mean time to failure.