Please help! And please explain how to get answers so I can learn how to do it on future problems. Thanks in advance! I'll be sure to give a thumbs up.

Last month when Holiday Creations, Inc., sold 38,000 units, total sales were $288,000, total variable expenses were $213,120, and fixed expenses were $37,600. Required: 1. What is the company's contribution margin (CM) ratio? Contribution margin ratio 2. Estimate the change in the company's net operating income if it were to increase its total sales by $1,900. Estimated change in net operating income