4. A sample of 25 ignition condensers for a Willys CJ-2A are chosen for life testing. The time to failure of the component is exponentially distributed. The test is terminated after 850 hours, with six failures being observed at times 600,650,680, 710, 740, and 755 hours. Failed items are not replaoed. 4.1. Estimate the mean life of the components. (2 points) S 4.2. Estimate the failure rate of the components. (1 points) 4.3. Find a 95% confidence interval for the mean life. (2 points) 4.4. Assume that each failed item is replaced with an identical unit. Find a 90% confidence interval for the mean life. (2 points)