Jai wants to sell his car. He parks it at the side of a busy road near his house. He puts a notice on the windscreen which reads, "Car for sale. Call 0400312879 for details." Jai received a call from Nabeela at the number on his notice. She asks Jai about the car, including its age, the number of kilometres on the odometer and the service history. She then asks him the asking price for the car. Jai responds to her question in this way, "Well, it is a good, reliable car, and I could not let it go for less than $7000." Nabeela replies, "That is very expensive for a car which has travelled 200,000 km. Would you take $5000 in cash for the car? I can bring the money today." "I am not sure," says Jai. "I was really hoping for more." "Ok," says Nabeela. "$6000 is my final offer, and I will pay you the money on Friday when I collect the car." Jai responds, "Friday is a public holiday, but we can meet on Monday and I will deliver the car then?" Has a valid contract been negotiated between Jai and Nabeela for sale of the car? Why or why not?