Inatech produces 4750 computer drives per day. Each day, a sample of 300 drivess is tested for a period of 120 operating hours each.

Inatech produces 4750 computer drives per day. Each day, a sample of 300 drivess is tested for a period of 120 operating hours each. During the test, 3 failed at 10 hours, 4 failed at 30 hours, 2 at 76 hours, and 4 failed at 86 hours. 

Enter the following numbers to two decimal places of precision. If the answer should be expressed as a percentage, omit the % sign.

What is the percentage failure rate?  

What is the mean time between failures in hours? 

If the mean time to repair a drives is 8, what is the percentage availability for a drives?