You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
Given a disfluent sentence, modify the sentence to it to its equivalent fluent form, preserving the meaning of the sentence.

Who did the Han Chinese want to help the Khitan no I mean the Mongols fight?
Solution: Who did the Han Chinese want to help the Mongols fight?
Why? The input initially means Khitan and then changes to Mongols, hence this is correct.

New input: A conservative no the liberal force that acts on a closed system has what kind of mechanical work?
Solution:
A liberal force that acts on a closed system has what kind of mechanical work?