Let U be a population of size N which is partitioned into 2 strata U1 and U2, of size N1 and N2, respectively. Let m = NH 21.6w yi and {aim = IVEJ 21.6% 95- denote the stratum means of a survey variable y in both strata. In stratum h, h = 1,2, we select a simple random sample without replacement Sh, of size nil, h, = 1, 2. The sample selection in Stratum 1 is independent from the sample selection in Stratum 2. (a) Suppose that. we want to estimate the difference D = 'y'm 'gU2. Propose an unbiased estimator of D (call it 5) and determine its variance. (b) Suppose that we want to estimate the product P 2 gm x gm. Propose an unbiased estimator of P (call it is) and determine its variance