A manufacturer of disk drives for notebook computers wants a MTBF of at least 50,000 hours. Recent test results for 10 units were two failures at 10,000 hours, one at 20,000 hours, and two more at 40,000 hours. The remaining units were still running at 60,000 hours.

Determine the following:

a) Percent of failures = ____________% (enter your response as a percentage rounded to one decimal place).

b) Number of failures per unit-hour = _____________ failures per hour (round your response to eight decimal places).

c) MTBF at this time in testing = ____________hours (round your response to the nearest whole number).