what are the law using in this case ?

QUESTION 2 Khalil instructed his agent Leman to buy 300 cartons of apple juice from Murah Hyper Mart as they were selling the juice at half price as part of a promotion. Leman forgot to do so and when he went to Murah Hyper Mart a few days later, the promotion has ended, and he had to purchase them at the normal price. Khalil became very angry with Leman and scolded him. Leman retaliated by immediately quitting from his post. Advise Khalil on the course of action available to him. (15 marks)