The secret message "ZAZEKKOBND$\_$E$"$ was sent using the usual numbering scheme given above $($there are $27$ characters in total, so you need to work modulo $27),$ but with an unknown encoding matrix. However, you happen to know that the first four letters of the plaintext message are "YOU $".$

$($Note: Space characters $""$ are shown as $"\_"$ to make them easier to see, but you should simply enter space characters as usual in your answer.$)$

Use this information to determine the encoding and decoding matrices, and then recover the plaintext.

The encoding matrix is $\backslash ($ A$=[\backslash )?$

The decoding matrix is $\backslash ($ A$^\{-1\}=[\backslash )$

The decoded plaintext is