Please help me with my stat sampling problem.

1. [16 points] A researcher seeks to estimate the average number of public school students enrolled per district in New Jersey for the school year 2009. During this period there are 735 school districts. The researcher breaks up New Jersey into three regions: Northern, Central, and Southern. The Northern Region has 210 districts, the Central has 175 districts, and the South has 350 districts. The researcher picks a simple random sample of 10 districts, separately, from each region, and finds the following sample results: Region Northern Central Southern Sample size (Number of districts) 10 10 10 Sample mean of enrollment 1600 2000 1800 Sample standard deviation of enrolment 700 900 1200 1) [4 points] Estimate the average enrollment per district in New Jersey. 2) [4 points] Give a bound on the error of estimation in Question 1).3) [4 points] Using the information from the sample, design a new survey that uses a total sample size of 80 districts to achieve the best possible precision for your estimate of the average enrollment per district. How many districts should be taken from the Northern Region, Central Region, and Southern Region? 4) [4 points] For the new survey in Question 3), instead of using the total sample size of 80, find the minimum total sample size for stratified sampling from the three regions to estimate the average enrollment per district in New Jersey with a bound of 200 on the error of estimation