What is the relationship between 'Aurizon' and 'coal' in the context of the input sentence.
Options: manufacturer, employer, product/material produced, operator

Prescott quietly slipped out of Aurizon last week, and the public formalities of Monday's obviously solid annual results announcement provided a timely platform for chief executive Lance Hockridge to reassert a recovery of focus on his core coal business and on sating senior owners' expectations that he is running an annuity investment.
product/material produced