Intelligence Contest #14 - Win 100% of the SBD + Free Votes

A new way to win SBD and Votes! Win my new Intelligence Contests!!! I will be posting them everyday at random times and you can win 100% of the SBD this post makes + a vote from me (I got 20 steempower + 180 delegated SP, so over 3 cents per vote.)

I have and will not have copied any of the puzzles I post from other websites. They are unique, so you can try using google, but you ain't gonna find the solution by simply clicking "Search this image on google". Just wanted to make that clear :P

You win if you are the first to comment the correct answer in the comments.

RULES:
-Upvote this post
-Comment your answer
-Do not edit your comment
-1 answer per comment
-No spam

Question

Today, John's nerd found a locked box. Obviously, John wants to know what's inside the box. The nerd took this picture of the lock:

In the lock, there's 1 empty square. John has to tell his nerd what letter it is. It initially allowed 3 attempts, but John's nerd wasted 2 of them on "a" and "b". You have only 1 chance to tell John the right answer! And because John's nerd messed up a bit, you have to fill in an additional row too!

So put in the comments what letter should be located in the ninth square AND which 3 letters should be added in the row below the current 3 rows. You got only 1 try.

PS: Add your logic! Maybe there are multiple solutions, so if you add your logic, it may be correct!

If you liked this contest, please Upvote(required to win prize), Resteem(not required) & Follow (For more!)