You have been hired by a college foundation to conduct a survey of graduates.

a. If you want to estimate the percentage of graduates who have made a donation to the college after graduation, how many graduates must you survey if you want 98% confidence that your percentage has a margin of error of five percentage points?

b. If you want to estimate the mean amount of all charitable contributions made by graduates, how many graduates must you survey if you want 98% confidence that your sample mean is in error by no more than $50? (Based on results from a pilot study, assume that the standard deviation of donations by graduates is $337.)

c. If you plan to obtain the estimates described in parts (a) and (b) with a single survey having several questions, how many graduates must be surveyed?