In this task, you're given an open-domain question. Your task is to provide an answer to the given question. There is only one unique answer for each question. Your answer should be short, and refer to an entity, date, number, etc. Do not put your answer in the context of a sentence.

How many episodes are on season 3 of empire?
18

How many series are there of the mentalist?
7

Where is the source of the murray river?

Australian Alps, NSW