AB is a common tangent of circles C, D, E and F. Suppose that AC = 12, DB = 9 and AE = BF = 3. If the midpoint of EF is the center of a circle that is tangent to both circles E and F, what are the possible values for its radius?

AB is a common tangent of circles C D E and F Suppose that AC 12 DB 9 and AE BF 3 If the midpoint of EF is the center of a circle that is tangent to both circle class=