A political candidate is anxious about the outcome of the election. (a) To have his next survey

Question:

A political candidate is anxious about the outcome of the election.
(a) To have his next survey result produce a 95% confidence interval with margin of error of no more than 0.025, how many eligible voters are needed in the sample?
(b) If the candidate fears that he’s way behind and needs to save money, how many voters are needed if he expects that his percentage among voters p is near 0.25?