The probability density function for the time to failure in years of the drive train on a Rapid Transit Authority bus is given by f(t) = 0.2 - 0.02t O:::;t:::;lOyr (a) If the bus undergoes preventive maintenance every 6 months that restores it to as good as new condition, determine its reliability at the end of a IS-month warranty. (b) Compute the MTTF under the preventive maintenance plan in part (a)