An offer refers to any proposal to enter into a contract with one or more specific people, if its content is very certain, and it shows that the offeror has the intention to be bound by its offer once it is promised. Typical Case 2016 6 On the 8th, Party A sent a telegram to Party B, "I have a batch of canned grapes here, do you need it?" The next day, Party B received a call back: "Need, please inform us of the goods and the price. " On June 13, the power generation details: "1500 cans of grapes, 545 grams of tin tin, 20 bottles per box, the unit price of 2.10 yuan per bottle, the quality in line with national standards, the entire batch of freight plus 1,200 yuan. " Later, the call back requested to change the tin 545 g type to 300 g type, and requested delivery in mid-August, and payment was made upon seeing the manifest. On June 17, Party A considered that the quantity of the 300 g type in its inventory was small. Difficulties in delivery in the middle of the year, could not meet the needs of Party B, so the power generation told Party B: "We only have 545 grams of goods, can be delivered in mid-August. " We agree, please also consider the size of 300 grams of tin. ". According to the definition above, how many offers are in the above case? ['.', '.', '.', '.']