Let the circles \( C_1 : (x-\alpha)^2 + (y-\beta)^2 = r_1^2 \) and \( C_2 : (x-8)^2 + \left(y-\frac{15}{2}\right)^2 = r_2^2 \) touch each other externally at the point \( (6,6) \). If the point \( (6,6) \) divides the line segment joining the centres of the circles \( C_1 \) and \( C_2 \) internally in the ratio \( 2:1 \), then \( (\alpha+\beta) + 4(r_1^2 + r_2^2) \) equals:
