Let C1 , C2 be two circles touching each other externally at the point A and let AB be the diameter of circle C1 . Draw a secant BA3 to circle C2 , intersecting circle C1 at a point A1 (≠A), and circle C2 at points A2 and A3 . If BA1 = 2, BA2 = 3 and BA3 = 4, then the radii of circles C1 and C2 are respectively
