Answer: B
The margin of error is equal to 20
![M\mathrm{}E=20](https://img.qammunity.org/2023/formulas/mathematics/college/yya0qylnlelk1qm7g43yx4lgox8t526dol.png)
Step-by-step explanation:
Given that the 80% confidence interval is found to be;
![(200,240)](https://img.qammunity.org/2023/formulas/mathematics/college/drwh199tej2lnqpq8qjmijvaqn8cffhof6.png)
The width of the interval is;
![240-200=40](https://img.qammunity.org/2023/formulas/mathematics/college/x38x1xtwy9ypthh2nf9a0s0li9rir4zgp9.png)
The margin of error is always half the width, so the margin of error is;
![\begin{gathered} M\mathrm{}E=(40)/(2) \\ M\mathrm{}E=20 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/hfe87sd6uvn9h41wdgopytdrmahc5jfof5.png)
Therefore, the margin of error is equal to 20