Rachel wishes to install a new door for her home. She engaged a contractor called "Durable Doors" ("DD") for this purpose. Under their contract, DD will be paid a total amount of $1,500 for the project, which consists of $500 for DD to come up with an original design (which will be painted on the door), and $1,000 for the manufacture and installation of the door.

A few days after the contract was signed, DD prepared and presented some original design proposals to Rachel, and Rachel eventually agreed on a design with a pattern comprising tulip flowers and leaves. Subsequently, DD's representatives also visited Rachel's home to take measurements, and the parties agreed that the door will be manufactured at the specifications of 200 centimetres by 80 centimetres.

DD proceeded to manufacture the door, and their representatives visited Rachel's home a week later to install the door. At the time of installation, DD's representatives found out that the door measured 199.5 centimetres by 80 centimetres, which deviated slightly from the agreed specifications. However, the slight deviation did not affect the installation or function of the door. Rachel also discovered that the painted pattern on the door showedroseflowers and leaves, instead oftulipflowers and leaves. Visually, they looked quite different. However, DD did not want to rectify this painting defect.

Examine whether the contract between Rachel and DD has been discharged by performance, and conclude whether DD is entitled to any payment for the work that it has completed. In your answer, you should discuss the precise performance rule and all of the exceptions. (25m)