2. The table below gives, for each of three regions , the number of parks it contains, an estimate of the standard deviation of the number of rare trees growing within each park in that region, and the sampling cost per park within the region . Number of Estimated standard Sampling cost parks deviation per park 15 13 5 12 13 'i' 'i' 8 3 Find the stratum sample sizes required to estimate the average number of em- ployees in companies over all towns, if we allow a standard error in this estimate of 3.0, given that the total east of sampling is to be minimised