Utilize the input text as a context reference, choose the right relationship between Walter Energy and coal from the options. Options: 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