Elementary Statistics (12th Edition)

$\mu$ is between 8.156 and 11.46.
Given mean:9.808. Given $\sigma$:5.013. $\alpha=1-0.98=0.02.$ $\sigma$ is known, hence we use the z-distribution using the table. $z_{\alpha/2}=z_{0.01}=2.33.$ Margin of error:$z_{\alpha/2}\cdot\frac{\sigma}{\sqrt {n}}=2.33\cdot\frac{5.013}{\sqrt{50}}=1.652.$ Hence the confidence interval:$\mu$ is between 9.808-1.652=8.156 and 9.808+1.652=11.46.