Dr Jing signs a contract to buy David's house for $700,000 but the contract has an express clause which says the purchase only goes ahead if the local government department approves Jing's plans to convert the house to professional medical rooms. The local government department rejects Dr Jing's plans. Does a contract exist which allows David to enforce the agreement and require Dr Jing to go ahead with the purchase? You must explain your answer using legal terms; just saying Yes or No will not get marks. [2 marks]