Rav and Shmuel discuss the differences in when the merchandise is acquired if you say I am buying all of it for one price or if you specify how much each measurement (for ex. each se’ah) will cost (even though you are buying many se’ah). Two sources are brought to contradict their opinion but are resolved. The next mishna discusses 3 different halachot – one pertaining to at what point of measuring is neither side allowed to change their mind, the next pertained to a middleman – and is he responsible if the vessel breaks and the merchandise is lost (wine or oil) (exactly what the case is is debatable), and what is the status of drops left in the jug after if it measured out and poured into the buyers utensils? Details of these cases are discussed int he gemara. The next mishna is a case where a father sends a son to the store to buy oil and the utensil breaks, the oil is lost, as is the change that the son received. There is a debate about who is responsible. Based on details in the mishna, the gemara grapples to understand what exactly is the case in the mishna and what is the source of the debate.