can you please answer this question..

For each of the following encryption schemes, state whether the scheme is perfectly secret. Justify your answer in each case.

(a) The message space is M = {0, . . . , 4}. Algorithm Gen chooses a uniform key from the key space {0, . . . , 5}. Enck (m) returns [k + m mod 5], and Deck(c) returns [c ? k mod 5].