In this task, you're given an ambiguous question (which can be answered in more than one way). Your task is to provide one question which clarifies the input question and it has one unique answer, and also provide an answer to the generated question. Generated question and answer should be separated with a new line.

Who made the first periodic table of elements?
Who made the first recognizable periodic table of elements? 
 Dmitri Mendeleev

How many copies did back in black sell?
About how many copies did back in black sell worldwide? 
 50 million copies

How many episodes of ncis have there been?

How many episodes of ncis have there been by the end of 2017? 
 340