Definition: In this task, you will use your knowledge about language (and common sense) to determine what element the marked number refers to. The numbers are marked with two underlines around them, like: _ number _. Your answer should be chosen from the given text, and should not contain other words.
Input: Batman:  Catwoman 's up there , and she 's about to make off with a bundle if we let her .
Commissioner Gordon: But Batman , we still do n't know what she 's stealing .
Batman: Eight pieces of catgut .
Chief O'Hara: How much could they be worth ?
Batman: Plenty ! They 're attached to two Stradivarius violins . Each _ one _ is being sold today for a quarter of a million dollars .

violins