Edgbaston Athletic are a football team playing in the lowest division of the Football League. They agree to sell their best striker, Dwayne Mooney, to Premier League club Birmingham United. The terms of the sale are that United will pay Athletic 750,000 immediately for the player, and then a further 250,000 when Mooney has scored 20 goals for his new club. When playing for Athletic, Mooney scored 126 goals in 166 matches. At United, Mooney scores 5 goals in 13 matches between October and December 2015. A new manager is appointed at United in January 2016. Mooney is sold to another club a month later, having scored only 1 further goal in 7 matches. The contract between United and Athletic makes no provision for what is to happen if the player is sold before scoring 20 goals.

(a) Is United contractually bound to pay 250,000 to Athletic?

(b) draft an express contract term to deal with the situation that has arisen.