Based on past experience, a company has developed the following budget formula for estimating its shipping expenses. The company's shipments average 12 lbs. per shipment:

Shipping costs = $16,000 + ($0.50 x lbs. shipped)

The planned activity and actual activity regarding orders and shipments for the current month are given in the

following schedule:

                           Plan     Actual

Sales orders              800      780

Shipments                800      820

Units shipped            8,000    9,000

Sales                 $120,000   $144,000

Total pounds shipped    9,600    12,300

The actual shipping costs for the month amounted to $21,000. The appropriate monthly flexible budget allowance for shipping costs for the purpose of performance evaluation would be

A. $20,680

B. $22,150

C. $20,800

D. $20,920