A trial is set to start in Denver on Monday determining whether or not a multi-billion dollar grocery merger will be allowed to move forward.

The trial for the case brought forth by Colorado against the parent companies who run King Soopers and Safeway stores across the state will begin on Monday — marking the start of the third trial attempting to block the proposed $25 billion deal.

Colorado Attorney General Phil Weiser says the chains monitor each other’s prices and that when there’s little competition, prices for groceries go up.