A manufacturer of disk drives for notebook computers wants a MTBF of at least 50,000 hours. Recent test results for 10 units were one failure at 10,000 hours, one more at 25,000 hours, and two more at 45,000 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).