Exercises 38: Let us define a new stream cipher. The cipher is affine, but the keys depend on the position of the character in the plaintext. If the plaintext character to be encrypted is in position n, we can find the keys as follows:

(a). The multiplicative key is the (n mod 12)-th element in Z_26* ;

(b). The additive key is the (n mod 26)-th element in Z₂₆ ;

Encrypt the message cryptography is fun using this new cipher

It is Cryptography Course

please I need the detailed answer (steps how to get the answer)