In the below scenario, in reference to the common law of contract, is Tom bound by his promise that he wouldn’t demand the $10 000 shortfall?

Jared owes Tom, the timber merchant, $110,000 for timber Tom has supplied for the flooring in the house.

Jared tells Tom that he’ll recommend the timber yard to all his building colleagues, if Tom will accept $100,000 in full payment of the debt.

Tom agrees to accept the lesser amount, and promises not to demand the $10,000 shortfall.

Tom doesn’t notice any increase in business over the next month, so Jared and demands the $10,000.