The circle S = x2 + y2 − 2x − 4y + 1 = 0 cuts the y-axis at A, B (OA: OB). If the radical axis of S ≡ 0 and S′ = x2 + y2 − 4x − 2y + 4 = 0 cuts the y-axis at C, then the ratio in which C divides AB is: