You are given a ciphertext that you are told was encrypted with one of the three historical encryption methods: transposition cipher, monoalphabetic cipher, polyalphabetic cipher. You are also told that the plaintext is an English language document. Concisely explain how you can use the single letter frequencies of the ciphertext letters to help you to determine which encryption method may have been used. For each encryption method, explain whether using only single letter and bigram/trigram frequencies are sufficient to cryptanalyse a ciphertext.