Minden Company manufactures a high-quality wooden birdhouse that sells for $25 per unit. Variable costs are $12 per unit, and fixed costs total $210,000. The company sold 30,000 birdhouses to customers during 2020. The president of Minden Company believes the following changes should be made in 2021: 1. the selling price of the birdhouse should be reduced by 20% 2. increase advertising by $33,000 Assume these changes are made. Calculate the number of units Minden Company must sell in 2021 in order to earn a net income that is 40% larger than the net income earned in 2020.