Use the Table the Cost of Swing Sets

Use the table The Cost of Swing Sets. Eleanor's costs of producing swing sets are given in this table, but the labels for several columns are missing. What is true if she can sell four swings for $3,000?

A) She is making a profit.
B) Her marginal product of labor is decreasing at the fourth swing.
C) Her average total cost is $150.
D) Her marginal cost is greater than her variable cost.