If the points of intersection of the ellipses \( x^2 + 2y^2 - 6x - 12y + 23 = 0 \) and \( 4x^2 + 2y^2 - 20x - 12y + 35 = 0 \) lie on a circle of radius \( r \) and centre \( (a,b) \), then the value of \( ab + 18r^2 \) is:
\( 51 \)
\( 52 \)
\( 53 \)
\( 55 \)