Doubleday Inc. sells a single product with a selling price of $120 per unit. The company's variable cost per unit is $78 and its total fixed costs are $130,000. During the month of April, the company sold 6,000 units. Management expects that its sales will increase by $15,000 in May. Assume that the selling price per unit, variable cost per unit and total fixed costs remain constant for the month of May. What is the dollar increase in net operating income in May if management's expectation is realized? \begin{tabular}{l} $2,100 \\ $5,250 \\ \hline$3,900 \\ $9,750 \end{tabular}