Could I get an explanation or formula to determine the highlighted field (ending inventory)?

Boise, Inc., planned and actually manufactured 180,000 units of its single product in 2017, its first year of operation. Variable manufacturing cost was $13 per unit produced. Variable operating (nonmanufacturing) cost was $10 per unit sold. Planned and actual fixed manufacturing costs were $720,000. Planned and actual fixed operating (nonmanufacturing) costs totaled $360,000. Boise sold 120,000 units of product at $36 per unit. Read the fequirements Requirement 1. Boise's 2017 operating income using absorption costing is (a) $720,000, (b) $480,000, (C) $840,000, (d) $1,080,000, or (e) none of these. Show supporting calculations. Revenues $4,320,000 Cost of Goods Sold Beginning Inventory 0 Variable manuf. costs $ 2,340,000 Allocated fixed manf costs $ 720,000.00 Cost of Goods Available For Sale $ 3,060,000 Deduct Ending Inventory ???? Cost of goods sold #VALUE! Gross margin #VALUE! Variable operating costs $1,200,000 Fixed Operating Costs $360,000 Operating Income #VALUE