Respuesta :
C. a proposal from a local radio station detailing a popular ad
Because those holding the bake sale would know how much they are charging sponsors for sponsorships and would also know the number of people who would come into contact with the sponsor information, the information that would be needed is the same information for a radio ad campaign in order to make the comparison. As such a proposal from a local radio station detailing a popular ad plan would be just the source needed.
Answer: a proposal from a local radio station detailing a popular ad
Explanation: got it right on the lesson