Refer to the input text as context and select the correct relationship between 'Walter Energy' and 'coal' from the available options.
Options: owned by, distributed by, product/material produced, business division

Walter Energy Inc. (WLTGQ), with its restructuring deal in pieces, pleaded with a reluctant bankruptcy judge Thursday for a new cash order that would appease its lenders and grant the coal company 30 days to reset.
product/material produced