Use the information provided below to answer the following questions: Sales ($50 per unit) $10,000 Cost of goods sold (all variable costs) 6,000 Fixed costs 2,800 a. How many units would the company need to sell to earn $4,000 in operating income? b. How many units would the company need to sell to earn $4,000 in net income if the tax rate is 20%? C. By how much would operating income change from part (b) with a 10% increase in units sold