Molly runs a shop with two products. Product A has a unit contribution margin of $300 and Product B has a unit contribution margin of $100. In January she sold a total of 2,000 units with Product A making up 20% of total sales and Product B making up 80% of total sales. In February she sold 1,800 units, with Product A making up 30% of sales and Product B making up 70% of sales. In March she sold 1,500 units, with Product A making up 50% and Product B representing 50%. Fixed costs and unit contribution margins remained constant from January through March. During which month was Mollys net income the highest?

I know the answer is March.

I want to know how to get to the answer. Please show the steps.