Determine the sample size of the following problems. Show your solution.

1. A dermatologist wishes to estimate the proportion of young adults who apply sunscreen regularly before going out in the sun in the summer. Find the minimum sample size required to estimate the proportion with precision of 3%, and 95% confidence.
2. The administration at a college wishes to estimate, the proportion of all its entering freshmen who graduate within four years, with 90% confidence. Estimate the minimum size sample required. Assume that the population standard deviation is = 1.3 and precision level is 0.05.
3. An internet service provider wishes to estimate, to within one percentage error, the current proportion of all email that is spam, with 90% confidence. Last year the proportion that was spam was 71%. Estimate the minimum size sample required if the total email that is spam is 10,000.