The results of testing recently redesigned bus components shows that the axle has a mean "time" between failures of 600,000 miles, the modified electric motor controller has a mean "time" between failures of 740,000 miles, and the anti-lock braking feature has a mean "time" between failures of 650,000 miles. If failure of any one of these com- ponents results in failure of the bus, what is the probability that a bus will fail before it accumulates 500,000 miles? Assume that the failures of these three components are the only remaining causes of bus failure, and that the failures rates are constant.