B. $30,000 is the total variable overhead at the level of 1,000 direct labor hours.

C. This is the total factory overhead allocated in the middle month, February, divided by the number of direct labor hours used during February, and multiplied by the number of direct labor hours used in January. This is not the correct way to estimate fixed cost.

D. The best method to use to separate variable and fixed factory overhead costs is the High-Low Points method. First, calculate the variable portion of the cost. This is done by dividing the difference between the highest and the lowest total factory overhead costs by the difference between the number of units of the associated direct labor hours. The result is the variable cost per unit: