Tom contracts with Jerry to paint Jerry's house for $4,500. When the job is less than half finished, Tom gets a great job offer in Adelaide and tells Jerry "I'm sorry I can't finish your job as I have accepted another job offer in Adelaide".

Jerry is very worried about being able to move into his house on time and says to Tom "I'll pay you an extra $1,000 if you can finish painting the house before you go to Adelaide."

Tom agrees to this proposal and finishes Jerry's house as promised. Jerry pays Tom only $4,500 and refuses to pay the other $1,000.