The circle C1 and C2 are externally tangent to each other at T. A line passing through T meets C1 at A and meets C2 at B. The line which is tangent to C1 at A meets C2 at D and E. If D∈[AE], ∣TA∣=a, ∣TB∣=b, what is ∣BE∣?<spanclass=′latex−bold′>(A)</span>a(a+b)<spanclass=′latex−bold′>(B)</span>a2+b2+ab<spanclass=′latex−bold′>(C)</span>a2+b2−ab<spanclass=′latex−bold′>(D)</span>a2+b2<spanclass=′latex−bold′>(E)</span>(a+b)b