Solution:
Given:
[tex]C.I=(120,140)[/tex]
The margin of error is equal to half the width of the entire confidence interval.
Hence, the width of the confidence interval is;
[tex]140-120=20[/tex]
Hence, the margin of error is half the width of the confidence interval.
[tex]\begin{gathered} margin\text{ of error}=\frac{20}{2} \\ margin\text{ of error}=10 \end{gathered}[/tex]
Therefore, OPTION B is the correct answer.
