Brent owns property on Whidbey Island. He makes a written contract with Jennifer to draft plans for a house he wants to build on the property. The contract requires that she complete the plans in a form ready to submit to the City Building Department for $3,000 by November 1st. Before she finishes she receives a rush order for some other plans for $1,500. She does not want to give up this opportunity to make more money. She tells Brent she would only finish his plans by November 1st if he agreed to pay $1,500 more to cover her not being able to do this other project. Brent agrees but does not know where he will get the additional money to pay her. They put in writing that he will pay her $1,500 more to do what she promised in the initial agreement. She finished the plans by November 1st and billed Brent for $4,500. Brent only pays $3,000. If Jennifer sues Brent for the remaining $1,500 will she win? Determine the legal principles involved and discuss who wins and how much.