Habib operates an outsourcing institute where he charges Tk. 5000 for one month's training. Last month 30 people took the training and all of them except Rahat, paid the full amount after completing all training courses. Rahat requested Habib to give him two weeks' time so that he can pay the amount. - Which type of contract it is? (among Habib and other trainees as well as between Habib and Rahat) Give logic.