It goes like this: There are two stables on a farm, one that houses 20 horses and 13 mules, the other with 25 horses and 8 mules. Without any pattern, animals occasionally leave their stables and then return to their stables. Suppose that during a period when all the animals are in their stables, a horse comes out of a stable and then returns. What is the probability that the next animal coming out of the same stable will also be a horse?
I'm thinking Bayes' Rule will come into play here some how but I'm not sure.