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:

a. \(\$ 12,500\)

c. \(\$ 7,500\)

b. \(\$ 8,000\).

d. Some other amount.