TASK $3(3$ points each, total $6$ points$)$

Here is another encryption$/$decryption exercise. For this exercise, I have provided a word that will serve as the

key. You must figure out the key in order to complete this section.

To get you started: Easy $=$ CDRA $($Once you figure out the pattern to this, you can do the following$)$:

$3$a$.$ Encrypt this plaintext:

Cryptography is the art of secret writing.

$3$b$.$ Decrypt the following ciphertext:

ALVAC KPLNV GGIEU RJBXY AVPSR OBAVF DC