13.15 Twelve units were placed on test. The test was terminated after eight failures had been obtained (Type II). In addition, two units had to be removed prior to their failure or the termination of the test. The following failure and censor times were recorded: 3 50 65 157 244 245 341 382 710' 945 (a) Find the MLE for the MTTF for the exponential distribution. (b) Find the MLEs for the Weibull distribution. (c) Find the MLEs for the lognormal distribution.