Montclair Company earns an average contribution margin ratio of 40% on its sales. The local store manager estimates that he can increase monthly sales volume by $45,000 by spending an additional $7,000 per month for direct mail advertising. Compute the monthly increase in operating income if the manager's estimate about the increased sales volume is accurate.

1. $11,000
2. $18,000
3. $23,000
4. $16,000