What is the relationship between Walter Energy and coal in the context of the input sentence. Choose an answer from: product/material produced; manufacturer; distributed by; industry; position held; original broadcaster; owned by; founded by; distribution format; headquarters location; stock exchange; currency; parent organization; chief executive officer; director/manager; owner of; operator; member of; employer; chairperson; platform; subsidiary; legal form; publisher; developer; brand; business division; location of formation; creator.

Walter Energy Inc.’s most senior lenders are pushing the unprofitable coal miner to slash worker pay, reduce pension expenses and idle plants as part of a bankruptcy plan that they will present the company this week, according to three people with direct knowledge of the matter.

Answer: product_or_material_produced