Consider the following two-stage stratified sampling plan. In the first stage, the population is stratified into H strata and kh clusters are selected from stratum h with probability proportional to cluster size, where sampling is independent across strata. In the second stage, a sample of mhi units is selected from sampled cluster i in stratum h, and sampling is independent across clusters. Find πi and the Horvitz Thompson estimator Yht of the population total.