At the beginning of the year, X Company expected to produce 3,500 units of its only product. Its estimate of fixed overhead was $15,000, and its estimate of variable overhead per unit was $6.52. At the end of the year, 2,500 units were actually produced, with actual total overhead cost of $30,137. 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: $1,163 B: $1,454 C: $1,817 D: $2,271 E:$2,839