I have answers, I need step by step solution please :) I dont understand where 204750 come from.

5. Ralph Co. produced and sold 180,000 units of products in 2022 and prepared the following contribution margin income statement. Sales Variable expenses 8,640,000 6.480.000 Contribution margin 2,160,000 Fixed expenses Net income 600,000 1,560,000 Required: (1) What is Ralph's margin of safety in units? (2) Determine the sales revenues that ensures the pretax profit of $1,800,000 assuming the tax rate is 28%. (3) How many units should Ralph produce and sell that yields the after-tax profit of $1,337,040 assuming the tax rate is 28%.