Question $52(2$ points$)$

Suppose the following Caesar Cipher wheel is used to encode and decode messages:

The plaintext characters are on the outside of the wheel, and the ciphertext

characters are on the inside of the wheel. Two digits are used for each number.

Thus, to encrypt the plaintext message "SUM" we first convert the message to the

string "YAS" and then convert this to the numeric value $"240018".$

A simple encryption scheme is:

For encryption use: $c=(m+k)modN$

For decryption use: $m=(c-k)modN$

Let $k=21472$ and $N=30197.$ Use the scheme above to find the ciphertext for the

plaintext message "SUM".