Can you explain this to me$?$ I have no idea how to do this. Thanks

Net Income Planning Nolden Company has charged a selling price of $20 per unit, incurred variable costs of $12 per unit, and total fixed costs of $100,000. What unit sales volume is necessary to earn the following related amounts of net income before income tax? (a) $18,000,' (b) $27,000; or (c) (a) 14,750 (b) 15,875 (c) 25,000 Check units units units