The following failure times, in days, were obtained after placing 30 units on a 100-day testbed: 8, 12, 22, 51, 73, 85. (a) Determine the empirical reliability at 100 days. (b) Assuming a constant failure rate, find the MLE for the MTTF, and then find R(100). (c) Using (b), derive a 90 percent confidence interval for the MTTF. (d) Find R(100) from the least-square estimator for the MTTF. (e) Find the MLEs for the two-parameter exponential, and then estimate R(100) on the basis of the two-parameter model