Your source of rep is the association bonus, which is ignored when the check for protected questions is done. Hence, you cannot answer. This has been marked as status-by-design over here Stack Exchange doesn't allow me to answer protected questions because I gave away earned rep in bounties
Maybe you tried to post your answer as a comment as the privilege that requires 50 reputation points is comment everywhere. new user restrictions, including answering protected questions, are lift when a user reach 10 reputation points.
Please read the first link to learn about how comments should be used on this site.
How do I write write a good ...