The size of an animal population is sometimes estimated by the capture-recapture method. In this method, n1 of the animals are captured in the area under consideration, tagged, and released. Later, n2 of the animals are captured, X of them are found to be tagged, and this information is used to estimate N, the total number of animals of the given kind in the area under consideration. If n1 = 3 rare owls are captured in a section of a forest, tagged, and released, and later n2 = 4 such owls are captured and only one of them is found to be tagged, estimate N by the method of maximum likelihood.