The time to failure T of a microwave oven has an exponential distribution with pdf If three

Question:

The time to failure T of a microwave oven has an exponential with pdf

If three such microwave ovens are chosen and t is the mean of their failure times, find the following:
(a) Distribution of T-bar.
(b) P T-bar > 2).

Distribution
The word "distribution" has several meanings in the financial world, most of them pertaining to the payment of assets from a fund, account, or individual security to an investor or beneficiary. Retirement account distributions are among the most...