MTH128 Chptr 8 sample size given standard deviation

1) You want to obtain a sample to estimate how much parents spend on their kids birthday parties. Based on previous study, you believe the population standard deviation is approximately σ = 27.3 dollars. You would like to be 95% confident that your estimate is within 2.5 dollar(s) of average spending on the birthday parties. How many parents do you have to sample? 2) SAT scores are distributed with a mean of 1,500 and a standard deviation of 300. You are interested in estimating the average SAT score of first year students at your college. If you would like to limit the margin of error of your 95% confidence interval to 25 points, how many students should you sample?