Coronado, Inc. calculated how many units it needed in order to earn net income totaling $67300 for the month. What calculation did Coronado perform?

a	[Variable costs +($67300/1-tax rate)] contribution margin ratio

b	[Fixed costs + ($67300/1+tax rate)] contribution margin ratio

c	[Fixed costs + ($67300/1-tax rate)] contribution margin per unit

d	[Variable costs + ($67300/tax rate)] contribution margin per unit