statistics

There are ten identical parts. When the life span of each part follows Ga(r,}\\)) and is independent to each other, answer the following questions. (1) The random variable Y is the sum of the life expectancy of these parts. Find the distribution of Y. (Write specifically what distribution it is (e.g.Normal distribution, binomial distribution, etc.)) (2) Find the distribution of Z = 22W (e.g. normal distribution, binomial distribution, etc.) (3) Use number (2) to nd the (1 - a) x 100% of confidence interval of A