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.

Voice of optimus prime dark of the moon?
Peter Claver Cullen

Who became famous by singing the blues during the jazz age?
Empress of the Blues

How many league titles does manchester united have?

20