A manufacturer of disk drives for notebook computers wants a MTBF of at least 50,000 hours. Recent test results for 12 units were one failure at 12,000 hours, two at 20,000 hours, and one more at 40,000 hours. The remaining units were still running at 60,000 hours.
A) Number of failures per unit-hour =_____failures per hour (round your response to eight decimal places)
B) The mean time between failures (MTBF) is the expected time between a repair and the next failure of a component. MTBF at this time in testing =_______hours