Hello, we are trying to solve a problem for which we would appreciate any reference that you could give us. The problem is as follows. We have two urns. Each urn contains balls in different colors. The exact number of balls of each color in each urn is known. Imagine that we extract a number N of balls from these two urns, but we don’t know which balls have been extracted from which. We would like to know how many have been drawn from urn 1, and how many from urn 2. We are wondering whether this is something standard in statistics, or whether it is an application that someone has solved before. Any hints appreciated!