the ciphers in the following problem use this alphabet of 10 digits, 26 letters, and 3 punctuation marks - 39 charactters is all

0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ

a) use calculator but show all work- Decrypt the message ??KYYHV7XBSU. It was encrypted using an affine cipher. What key was used to encrypt? First three characters of plain text is 221

b) use computer- Same alphabet as a). Decrypt the message that was encrypted with a caesar cipher. W?YY?~.X112T3. Key is unknown

c) Explain what you can do to find the length of they keyword for a vigenere cipher, If you are given a substantial amount of ciphertext. Feel free to explain using an example.