Please help solve

"As the legend tells, Isaac Newton discovered the law of universal gravitation after an apple fell on his head. What happened with this great apple after it bounced off Newton's head?" People who visited a certain website were asked this question. Of 231 people who answered this question during the last month, 28% replied that Newton ate the apple. Calculate the margin of error for this result. Round the percentage to one decimal place. Do not round intermediate steps. If 28% of 231 people replied that Newton ate the apple, the margin of error is % X