Gamma Ltd has a plant capacity of 20,000 units per month. Unit costs at a capacity are:

Direct materials $3.50

Direct labour $4.50

Variable overhead $2.5

Fixed overhead $1.5

Administration-fixed $0.5

Current monthly sales are 15,000 units at $12 each. Delta Ltd has contacted Gamma Ltd about purchasing 5000 units at $11 each. Determine the effect on profit for Delta Ltd if the special order is accepted.

A. Decrease by $ 10 000

B. Increase by $2 500

C. Decrease by $7 500

D. Decrease by $ 2 500