The Willsey Merchandise Company has budgeted $40,000 in sales for the month of December. The company's cost of goods sold is 30% of sales. If the company has budgeted to purchase $18,000 in merchandise during December, then the budgeted change in inventory levels over the month of December is:
a. $6,000 increase.
b. $10,000 decrease.
c. $22,000 decrease.
d. $15,000 increase.