Similar to our previous challenges for answering unanswered questions, we're continuing our monthly habit of rewarding the best answer to any old unanswered question in order to encourage people to engage into solving some of our old unsolved problems. Thus independent from our more question-centered weekly topic challenge, we'd like you to answer any question that was asked more than 3 months before the current month and that doesn't have an answer yet.
To check for eligible questions you can use the search function or this data query. The top-voted answer given each month will be rewarded a bounty of 100 points if it has a score of at least 3 or has been accepted.
