At the beginning of the year, X Company expected to produce 3,000 units of its only product. Its estimate of fixed overhead was $10,000, and its estimate of variable overhead per unit was $6.80.

At the end of the year, 2,800 units were actually produced, with actual total overhead cost of $30,179.

What was X Company's total overhead flexible budget variance for the year [a positive number means a favorable variance; a negative number means an unfavorable variance]?

A: $-1,139

B: $-1,515

C: $-2,015

D: $-2,680

E: $-3,564

F: $-4,740

Please help me with this question I am so stuck!