2. Let II denote the Vigenere cipher where the message space consists of all 3-character strings (i.e., M = {a, ..., z}}), and the key is generated by first choosing the period tt, {1, 2, 3} and then letting the key be a uniform string of length t (i.e., kt, {a, ..., z}' or {O, ..., 25}'). So, the key space is K = {a, ..., Z} U{a, ..., Z}? U {a, ..., z}". Question : Compute Pr[K = k] for k = a, k = ab, and k = abc