A manufacturer of disk drives for laptop computers wants to achieve a MTBF of at least 50,000 hours. Recent test results for 10 units were one failure at 10,000 hours, another failure at 25,000 hours, and two more failures at 45,000 hours. The remaining units were still running at 60,000 hours. Determine the following and show all work:
a. Percent of failures
b. Number of failures per unit-hour
c. MTBF