Net Income Planning Nolden Company has charged a selling price of $20 per unit, incurred variable costs of $15 per unit, and total fixed costs of $55,000. What unit sales volume is necessary to earn the following related amounts of net income before income tax? (a) $18,000; (b) $27,000;0 (c) equal to 20% of 5 ales revenue, (a) units (b) units (c) units