Faux Trees Company produces artificial Christmas trees. A local shopping mall recently made a special order offer; the shopping mall would like to purchase 230 extra-large white trees. Faux Trees Company is currently producing and selling 20,000 trees; the company has the excess capacity to handle this special order. The shopping mall has offered to pay $160 for each tree. An accountant at Faux Trees Company provides an estimate of the unit product cost as follows: Direct materials $51.61
Direct labor​ (variable) $3.80
Variable manufacturing overhead $1.00
Fixed manufacturing overhead ​$4.00
Total unit cost $60.41

This special order would require an investment of $5,000 for the molds required for the extra−large trees. These molds would have no other purpose and would have no salvage value. The special order trees would also have an additional variable cost of $8.26 per unit associated with having a white tree. This special order would not have any effect on the​ company's other sales. If the special order is​ accepted, the​ company's operating income would increase​ (decrease) by:

a. $15679 decrease.
b. $15,679 increase.
c. $16,708 decrease.
d. $10,679 increase.