Colleen Stevens is the North Carolina senior account manager for a national medical equipment manufacturer. Colleen has overall responsibility for the Southeast sales division. The division employs approximately eight sales representatives. Colleen's representatives sell equipment, but equipment maintenance is provided by the maintenance division, which is coordinated through the national headquarters. Colleen is most likely in charge of which type of strategic business unit (SBU)? a. Cost center b. Revenue center c. Profit center d. Investment center