***I only need help on 3 and 4 :)

Orion Iron Corp. tracks the number of units purchased and sold throughout each year but applies its inventory costing method at the end of the year, as if it uses a periodic inventory system. Assume its accounting records provided the following information at the end of the annual accounting period, December 31 Unit Transactions Units Cost a. Inventory, Beginning 300 $12 For the year: b. Purchase, April 11 900 10 c. Purchase, June 1 800 13 d. Sale, May 1 (sold for $40 per unit) 300 600 e. Sale, July 3 (sold for $40 per unit) f. Operating expenses (excluding income tax expense), $19,500 Required 1. Calculate the number and cost of goods available for sale Number of Goods Available for Sale units Cost of Goods Available for Sale 2. Calculate the number of units in ending inventory. Ending Inventory units