(a) If the sum of the roots of the quadratic equation $ky^2-11y+(k-23)=0$ is $\;\frac{13}{21}$ more than the product of the roots, then find the value of $k$.OR(b) If $x=-2$ is the common solution of quadratic equations $a x^2+x-3a=0$ and $x^2+bx+b=0$, then find the value of $a^2 b$.