Data concerning Runnells Corporation's single product appear below: The company is currently selling 6,000 units per month. Fixed expenses are $424,000 per month. The marketing manager believes that a $7,000 increase in the monthly advertising budget would result in a 100 unit increase in monthly sales. What should be the overall effect on the company's monthly net operating income of this change? A. increase of $8,000 B. increase of $1,000 C. decrease of $7,000 D. decrease of $1,000