![](https://cos-cdn.shuashuati.com/pipixue-wap/2020-1230-1107-56/ti_inject-812ce.png)
Olsen Auto Supply typically earns a contribution margin ratio of 40 percent. The store manager estimates that by spending an additional $5,000 per month for radio advertising the store will be able to increase its operating income by $3,000 per month. The manager is expecting the radio advertising to increase monthly dollar sales volume by: