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: $\pm\frac{1}{\sqrt {2281}}\cdot 100\%\approx\pm2.1\%$
b) Thus we can be $95\%$ confident that between $31-2.1=28.9\%$ and $31+2.1=33.1\%$ of American adults would be willing to sacrifice a percentage of their salary to work for an environmentally friendly company.
