21FA - 02 Secret Message

Polly the Penguin is writing Panda Panda secret messages. These are top secret messages so she writes them with a secret code. In Polly’s code each letter corresponds with a number: $a-1, b-2, …, z-26$. Polly chooses some integer $k$ to add to the number corresponding to each letter in her message. The coded message contains the letters whose numbers correspond to the letters in the original messa