Given phrases that describe the relationship between two words/phrases as options, extract the word/phrase pair and the corresponding lexical relationship between them from the input text. The output format should be "relation1: word1, word2; relation2: word3, word4". 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.

Alpha Natural Resources Inc., Walter Energy Inc., Patriot Coal Corp. and James River Coal Co. have filed for bankruptcy during the past 16 months after the price of coal used in steelmaking dropped 67 percent since 2011.

Answer: product_or_material_produced: Walter Energy, Coal; product_or_material_produced: Patriot Coal, Coal