• Simone owns five terraced houses which she is planning to rent to students. The houses all need complete electrical rewiring before they can be rented out. Simone engages Peter to do this work during August, at an overall cost of 5,000, payable on completion of the work. After rewiring two of the houses Peter finds that the work is more difficult than expected because of the age of the houses. On 20 August he tells Simone that he is using more materials than anticipated and that the work will take much longer than he originally thought. He asks for an extra 500 to cover the cost of additional materials. Simone agrees that she will add this to the 5,000. In addition, because she is anxious that the houses should be ready for occupation before the start of the university term, she says that she will pay an extra 1,000 if the work is completed by 15 September. Peter completes the work by 15 September, but Simone says that she is now in financial difficulties. She asks Peter to accept 5,000 in full settlement of her account. He reluctantly agrees, but has now discovered that Simone's financial problems were less serious than she made out and wishes to recover the additional 1,500 he was promised. Advise Peter.