Answer
See below.
Work Step by Step
The margin of error of a sample size $n$ is a $95\%$ probability that a sample lies within the margin of error which is $\pm\frac{1}{\sqrt n}\cdot 100\%$
a) Hence here the margin of error: $\pm\frac{1}{\sqrt {n}}\cdot100\%$ ($n$ is not given)
b) Thus we can be $95\% $confident that between $21-\frac{1}{\sqrt {n}}\cdot100\%$ and $21+\frac{1}{\sqrt {n}}\cdot100\%$ of the interviewers are turned off by a job applicant being arrogant.
