Need help with highlighted Exercise 1 and Activity 1

Pupil Text MEP: Codes and Ciphers, UNIT 11 Transposition 11 Transposition One method of encrypting messages is called ransposition. Amessage, for example THIS IS A MESSAGE. HI is written across the rows in a grid: ISA M To obtain the encrypted message, simply read down the columns: TIEGHSSEIASHSMAI To decrypt the message, do the reverse: write down the columns and read across the rows The security of this system lies in having to know the size and shape of the grid Example 1 You intercept the following message ASNEFOELBCVYNAWEEEOONASRNUTIYIEIDMT a) How many letters are there? b) What possibilities are there for the shape of the grid? c) Use the information from (a) and (b) to unscramble the message Solution a) 35 letters b) 5rows by 7 columns or 7 rows by 5 columns c 7 rows by 5 columns gives the grid: Reading along the rows, the message is ALWAYS BE SINCERE EVEN IF YOU DO NOT MEAN IT () | N | O | T | M