Suppose that the target population has???? = 12, 000 units distributed over three strata.

If the number of units in the three strata are ????1 = 4000, ????2 = 5000, and ????3 = 3000, determine the

(a) sampling proportions for a stratified random sample selected using proportional allocation.

(b) strata sample sizes for a proportional allocation sample when the overall sample size is to be ???? = 250.

(c) the cost of sampling when the initial cost is ????0 = $5000 and the costs associated with sampling a unit from each of stratum are ????1 = $5, ????2 = $5, and ????3 = $10.