The centers of three circles of 1unit radius each lies on a straight line, AB, A is a point on the circumference of first circle

The centers of three circles of 1unit radius each lies on a straight line, AB, A is a point on the circumference of first circle. Second circle touches the first and third circle, From point A, a tangent AE is drawn to third circle, touching third circle at E this tangent cuts second circle at C and D. find length of chord CD?

a) 7/4

b) 10/7

c) 4/3

d) 8/5