A $15-$cm$-$diameter, $40-$cm$-$high vertical cylindrical container is partially filled with $\backslash (25-\backslash$mathrm$\{$cm$\}\backslash )-$high water. Now the cylinder is rotated at a constant speed of $\backslash (20\backslash$mathrm$\{$rad$\}/\backslash$mathrm$\{$s$\}\backslash ).$ Which of the following most nearly gives the maximum height difference $\backslash ((\backslash$mathrm$\{$cm$\})\backslash )$ between the edge and the center of the free surface?

$11\mathrm{.}5$

$5\mathrm{.}4$

$7\mathrm{.}2$

$9\mathrm{.}5$