2. We write the English alphabet in block capital letters: A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U. V, W. X, Y, Z. a) D is homeomorphic to O but no 3rd letter is homeomorphic to these two. Find two other pairs of letters with this property. b) Which letters are not homeomorphic to any other letter