Final answer:
The encrypted message for "aa" using the given rules becomes 'bc'. Rule 8 is applied to change the first 'a' to a 'b' and the second 'a' to 'c'.
Step-by-step explanation:
The student's question is asking us to encrypt the message "aa" (which has the value m = 11) using a specific set of encryption rules. To solve this, we apply each given rule to the message. Firstly, per rule 8, we change the first letter in the word to the letter that comes right after it in the alphabet, which turns 'a' into 'b'.
The second part of rule 8 tells us to make the second letter in the word a 'c', so the second 'a' becomes 'c'. Finally, rule 8 asks us to change every 'a' into the twenty-first letter of the alphabet, which is 'u', but since there are no 'a's left, this does not apply.
However, both instances of rule 5 result in no change since the first letter is already 'm' and there are no vowels left to change to the first vowel in the alphabet. Thus, applying only rule 8, the encrypted message becomes 'bc'.