Problem $3$

Problem $19\mathrm{.}28$ The slender bar has a mass of $6$ kg $.$ The spring $(\backslash ($ k$=10\backslash$mathrm$\{$~N$\}/\backslash$mathrm$\{$m$\}\backslash ))$ is unstretched in the position shown. The bar is given a clockwise angular velocity of $\backslash (30\backslash \%\backslash )$ s$.$ What is its angular velocity in degrees per second when it has rotated through an angle of $\backslash (20^\{\backslash$circ$\}\backslash )?$

The answer is somehow $43\mathrm{.}2$ degrees$/$second but I don't understand how that is the answer. Please help.