subject is business law

Mr.Khalid went to an electronic shop to buy a Laptop. The salesman showed one laptop saying that it was new model from a famous brand and also said that one time charging of the laptop will be enough to continuously for 5 days. Attracted to the features of the laptop, Mr.Khalid bought that laptop for 800 RO. Once he started using it, he knew that with a single charging, it is working for 4 days, not 5 days. Mr.Khalid went to the shop where he purchased the laptop and reported the shop owner that it is working for 4 days, but not 5 days. Shop owner apologized for what has happened. i) Which essential element is involved in the given case? Explain that element. ii) Explain the nature of contract? What are the rights of Mr. Khalid? Discuss all the elements and then decide the case