Help please! I don't understand, can someone guide me through this problem

Mansfiel Office Equiptment manufactures and sells metal shelving. It began operations on July 1,2020. Revenues in 2020 were \$ $422,400 The selling price per unit and the purchase price per pound of direct materials were stable throughout the year. The company's ending inventory of finished goods is carried at the average unit manufacturing cost for 2020. Finsihed-goods inventory at December 31,2020 , was 1 Calculate direct materials inventory, total cost, December 31,2020 2 Calculate finished-goods inventory, total units, December 31, 2020 3 Calculate selling price in 2020 4 Calculate operating income for 2020 Data table Inventory data are as follows: Variable manufacturing cost are variable with respect to Variable marketing, distribution, and customer service cost are variable with respect to unit sold. Mansfiel Office Equiptment manufactures and sells metal shelving. It began operations on July 1,2020. Revenues in 2020 were \$ $422,400 The selling price per unit and the purchase price per pound of direct materials were stable throughout the year. The company's ending inventory of finished goods is carried at the average unit manufacturing cost for 2020. Finsihed-goods inventory at December 31,2020 , was 1 Calculate direct materials inventory, total cost, December 31,2020 2 Calculate finished-goods inventory, total units, December 31, 2020 3 Calculate selling price in 2020 4 Calculate operating income for 2020 Data table Inventory data are as follows: Variable manufacturing cost are variable with respect to Variable marketing, distribution, and customer service cost are variable with respect to unit sold