We need to use the formula to find Margin of Error but through the sample proportion, that is
We will use a 95% confidence interval, that is a z value of 1.96 (Search in a Normal distribution table)
A) For A our (proportion) is equal to 0.45. So applying the formula,
B) We make the same of point A, but change our proportion to 0.35
c) We need to calculate the SE through proportion for 0.1, that is
Then our Error is given by,