Need help with highlighted Exercise 5, 6 & 7

Pupil Text MEP: Codes and Ciphers, UNIT 1 Substitution Ciphers 1 Substitution Ciphers A substitution cipher is one in which letters are represented by other letters; it can be deciphered by someone knowing the order of the cipher alphabet used One method of hiding messages in this way was invented by Julius Caesar, Roman Emperor over two thousand years ago. It is known as the Caesar cipher To encode a message, for example THIS CODE WAS INVENTED BY JULIUS CAESAR take each letter, go three along the alphabet and use that letter instead (e.g. A goes to D) Plain CipherD So the message b WKLV FRGH ZDV LQYHQWHG EB MXOLXV FDHVDU Exercise 1 What does the following message say? JRQH WR ZDWFK KDUOHTXLQV. EDFN DW VHYHQ Note that you can shift by any amount, not just three Exercise 2 How many different ways of enciphering are there in this way (i.e. by how many different amounts can you shift our alphabet?) On the next page is a table with the alphabet shifted by all possible amounts. This is sometimes known as a Vigenere square Exercise 3 The following message uses one of the shifted alphabets from the Vigenere square. What does it say? BPQA PIA JMMV APQNBML JG MQOPB