Definition: In this task, you will be given a short story. One sentence from the story is chosen. Consider the events that happen before that sentence, or are likely to have happened before it. Does any of them directly cause it, or simply make it possible? You should write your answer in the form " A >causes/enables> B". Try to use phrases and sentences from the story to compose your answer when possible.
Input: story: Kelly works a job as a waitress. An elderly couple came inside the restaurant. She waited on them and helped them choose their food. They smiled at her as they left. Kelly discovered a twenty dollar tip for her hard work!
 selected sentence: Kelly discovered a twenty dollar tip for her hard work!

Kelly helped an elderly couple at a restaurant >Causes/Enables> Kelly got a twenty dollar tip