I couldn't solve this. You don't have to do the calculations for me, I would just prefer if someone could tell me what steps to take; I'm a bit unsure where to start off with this one. Thanks!

For question 4, show all calculations to justify your final answer.

4.A pollster wishes to determine the sample size needed to determine the confidence interval for the percentage of voters who intend to vote for a certain candidate. Since this is his first survey, there is no previous estimate of the percentage. How large should the sample size be if

A pollster wishes to determine the percentage of college students that are receiving grants. He wishes to be 90% confident that the estimate is within 5% of the true proportion. How large should the sample size be if

c)There is no estimate available of the sample proportion

d)A prior study shows that 78.4% of college students receive grants