Remember that
For a 95% confidence interval --------> the value of z=1.960
Find out the value of
[tex]Z\frac{s}{\sqrt{n}}=1.960(\frac{12}{\sqrt{36}})=3.92[/tex]therefore
[tex]\begin{gathered} 230\pm3.92 \\ 230+3.92=233.92 \\ 230-3.92=226.08 \\ therefore \\ The\text{ answer is} \\ (226.08,233.92) \end{gathered}[/tex]