Sales during the year were $500$ units. Beginning inventory was $400$ units at a cost of $$6$ per unit. Purchase $1$ was $200$ units at $$7$ per unit. Purchase $2$ was $100$ units at $$8$ per unit.Required:a$.$ Assume the periodic inventory system is used. Calculate cost of goods sold and ending inventory using FIFO method.b$.$ Assume the periodic inventory system is used. Calculate cost of goods sold and ending inventory using LIFO method.