Can someone help me explain this problem. I am having issues understanding it

Speed World Cycles sells high-performance motorcycles and motocross racers. One of Speed World's most popular models is the Kazomma 900 dirt bike. During the current year, Speed World Cycles purchased eight of these bikes at the following costs: On July 28, Speed World Cycles sold four Kazomma 900 dirt bikes to the Vince Wilson racing team. The remaining four bikes remained in inventory at September 30, the end of Speed World's fiscal year. Assume that Speed World Cycles uses a periodic inventory system. Required: a-1. Compute the cost of goods sold relating to the sale on July 28 and the ending inventory of Kazomma 900 dirt bikes at September 30 , using Average-cost method. a-2. Compute the cost of goods sold relating to the sale on July 28 and the ending inventory of Kazomma 900 dirt bikes at September 30, using First-in, first-out (FIFO) method. a-3. Compute the cost of goods sold relating to the sale on July 28 and the ending inventory of Kazomma 900 dirt bikes at September 30, using Last-in, first-out (LIFO) method. Complete this question by entering your answers in the tabs below. Compute the cost of goods sold relating to the sale on July 28 and the ending inventory of Kazomma 900 dirt bikes at September 30, using Average-cost method