Riley's Rugs has a unit selling price of $120, unit variable cost of $40, and fixed costs of $35,000 per month. Last month, Riley's sold 950 rugs. This month, Riley's wishes to raise the unit selling price to $135, but thinks only 900 units could be sold. If Riley's makes only these changes, the contribution margin will Increase by $15,000. decrease by $9,000. increase by $9.500. remain unchanged