She cries and says yes. After kissing the tears from her eyes, you blindfold her and lay out two open engagement ring boxes in front of her so that she can pick her own ring in the most natural, Bayesian way possible. You also have a third ring that didn't come in a box (a family heirloom) so you've added that ring into the left box, per pic related. What is the probability that the next ring she picks from a box will be the heirloom ring. (Note: She can't see into any of the boxes.)