Given the task definition, example input & output, solve the new input case.
Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.
Example: Sentence1: pesticides cause pollution. 
Sentence2: pollution can harm animals.
Output: pollution.
The word "pollution" is common to Sentence1 and Sentence2. So, it's a good answer.

New input case for you: Sentence1: Producers gain in terms of producer surplus. 
Sentence2: consumers can take in food by eating those that gain in terms of surplus.
Output:
surplus