Numbat Shire Council's environmental manager, Leo, was contacted by Graino, a local stock feed business, for help under the council's 'We are Here to Help' program. The council agreed to help eradicate vermin from Graino's storage facilities. However, after the council workers did their work, much of Graino's wheat and barley stock became contaminated, causing considerable loss to the business. To make things worse, Graino also responded to a council advertisement in the local newspaper that it would provide a rates discount to any local business that achieved certain environmental clean-up targets. But after Graino made some costly changes to its internal processes in an attempt to reach those targets, the council publicly withdrew the rates discount plan on its website.

What is the main issue here?

Apply relevant contract law.