Note that we can choose at most 2ℓ 1 + 2ℓ 2 ≤ t 1 • 2ε/(1 − ε) edges in total.
the number of choices of T 1 and T 2 is bounded above by For a given choice of T 1 and T 2 , for T to have small edge expansion, there must also not be too many edges that connect T 1 to vertices in V 2 − T 2 .