The circle through intersection of the ellipses is S1+λS2=0.
(1+4λ)x2+(2+2λ)y2−(6+20λ)x−(12+12λ)y+(23+35λ)=0.
For a circle: 1+4λ=2+2λ⇒λ=21.
Circle: 3x2+3y2−16x−18y+281=0⇒x2+y2−316x−6y+227=0.
Centre (a,b)=(38,3), r2=964+9−227=1847.
ab+18r2=38×3+18×1847=8+47=55.