Say that your best frenemy is using this encryption scheme. You accidentally find out that the encryption of the message MEET$\_$TUESDAY is PFGXCUWIVECB.

a$.(2$ pts$)$ Give the key that was used for this encryption.

b$.(2$ pts$)$ Why were you able to find the key without resorting to a brute$-$force attack?

c$.(2$ pts$)$ Which of the four attack models discussed in class does the scenario in this question correspond to$?$