A group students decided to conduct a survey at their college to find the proportion of freshmen who graduate. Please show the formula and values plugged in.

a. (4) What is the required sample size to estimate, with a margin of error of .1 and a 90% confidence level, the proportion of freshmen who graduate?

b. (2) To reduce the margin of error, a __________________ sample size should be selected. Please explain your rationale.