One of the external common tangent lines of the two externally tangent circles with center O1 and O2 touches the circles at B and C, respectively. Let A be the common point of the circles. The line BA meets the circle with center O2 at A and D. If ∣BA∣=5 and ∣AD∣=4, then what is ∣CD∣?<spanclass=′latex−bold′>(A)</span> 20<spanclass=′latex−bold′>(B)</span> 27<spanclass=′latex−bold′>(C)</span> 6<spanclass=′latex−bold′>(D)</span> 215<spanclass=′latex−bold′>(E)</span> 45 geometrygeometric transformationhomothety