3. We want to estimate the number of fish, say N, in a pond. We proceed as follows. We catch r fish and mark them. We then set them free. After some time, we catch n fish (without putting them back). Of these, X are marked. Consider r and n as constants we choose ourselves, and let X be the observation.
(i) Formulate a suitable statistical model.
(ii) Give an intuitively reasonable "estimate" of N based on the observation.
(iii) Answer the previous questions if, the second time we catch fish, they are put back directly after catching them (sampling with replacement).