Holly Inc. sells a single product for $$40.$ Variable costs include $$22$ for each unit plus a $10\%$ sales commission on each product sold. Fixed costs are $$105,000$ per month and they sell $21,000$ units per month. She wants to spend $$20,000$ on an advertising campaign that she believes will increase sales by $$50,000.$ What would be the effect on her net profits?

A$.$ $$2,500$ increase

B$.$ $$8,750$ decrease

C$.$ $$2,500$ decrease

D$.$ $$30,000$ increase