Take context from the input text and decide on the accurate relationship between 'Walter Energy' and 'coal' from the options provided.
Options: legal form, product/material produced, creator, platform

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.
product/material produced