(Solved): The Engine Manufacturer Above Has Observed That Their Engine Control Modules (ECM) Fail As A Direct ...

The engine manufacturer above has observed that their engine control modules (ECM) fail as a direct function of how many hours they are active. The mean time between failures for the ECM is 50,000 operating hours. Accounting has determined that the company cannot profitably afford to pay for the repair of more than 12% of the ECM modules produced.

Question: What do you estimate to be the maximum acceptable warranty period (in operating hours) so that the company does not end up having to exceed the guidance for acceptable fraction of units repaired under warranty?