please explain and show how you got the formula to get the answers.

Required information [The following information applies to the questions displayed below.) Trey Monson starts a merchandising business on December 1 and enters into the following three inventory purchases Monson uses a perpetual inventory system. Also, on December 15, Monson sells 29 units for $50 each. Purchases on Deceber 7 Purchases on December 14 Purchases on December 21 19 units @ $20.00 cost 36 units @ $30.00 cost 29 units @ $36.00 cost Determine the costs assigned to ending inventory when costs are assigned based on the FIFO method. Perpetual FIFO Goods Purchased Inventory Balance # of Units Date Cost Per Unit Cost of Goods Sold # of Cost Per Cost of Goods Units Unit Sold Sold Goods Purchased # of Units Cost Per Unit Inventory Balance December 7 December 14 December 15 Determine the costs assigned to ending inventory when costs are assigned based on the FIFO method. Perpetual FIFO: Goods Purchased # of Units Cost Per Unit Date Cost of Goods Sold # of Cost Per Cost of Goods Units Unit Sold Sold Goods Purchased Inventory Balance Cost Per Inventory # of Units Unit Balance December 7 December 14 December 15 December 21 Totals