A designer estimates that she can increase the average time

A designer estimates that she can increase the average time between failures of a part by 5 percent at a cost of $450. Currently, the average time between failures is 100 hours and the average repair time is 4 hours. (Round your \"Availability\" answer to 4 decimal places.) New MTBF hrs New MTR hrs Availability b. A designer estimates that she can reduce the average repair time by 10 percent at a cost of $200. Currently, the average time between failures is 100 hours and the average repair time is 4 hours. (Round your \"MTR\" answer to 2 decimal places and \"Availability\" answer to 4 decimal places.) New MTBF hrs New MTR hrs Availability c. Which option would be more cost-effective? Thus, the designer should choose method .

Solution

Current Availability = 100/ 105 +4 = .962

Increase in MTBF = (.05)(100) = 5 hrs.
New MTBF = 100 + 5 = 105 hrs.
Availability= 105/(100+4) = 105/109 = 0.9633

Reduction in MTR = (.1)(4 hrs.) = .4 hrs.
New MTR = 4 hrs — .4 hrs = 3.6 hrs.
Availability= 100 / (100+3.6) = 0.9653
Since .9653> .9633. designer should choose to reduce MTR.