The Simple Substitution Cipher is a major improvement on the Caesar Cipher (a) In what different ways is it an improvement? (b) If a Simple Substitution Cipher is used (with an unknown key) and we inter- 3. cept the ciphertext OXAO, then which of the following four-letter words could be the plaintext: JOHN, SKID, SPAS, LOOT, PLOP, or OSLO? (c) If a Simple Substitution Cipher is used (with an unknown key) and we inter- cept the ciphertext BRKKLK, then what do we know about the plaintext? (d) Suppose in the case of intercepting BRKKLK we also know the plaintext is the name of a country. What is the plaintext? (e) What important lesson does the BRKKLK example illustrate