Pomona Sporting Goods, Inc. (PSG), sponsors an annual Triathlon with an advertised first prize of $5,000. The rules require the competition to begin with running up to the top of Mount Baldy. Another rule says the PSG can change the terms of the competition at any time. Conchita enters the race and is declared the winner. PSG offers her a prize of $1,000 in lieu of $5,000. What law(s) apply here?