You Are the Senior Financial Analyst Supporting the Marketing Department

You are the senior financial analyst supporting the marketing department in your company, and head of marketing has asked you to come up with one performance metric that can be used to evaluate how effective each marketing campaign is in terms of contribution to the firm's profits. It should be a metric that can be easily used to compare different marketing campaigns against each other.
In response, you propose using:

A) A metric that takes the total new sales dollars generated by a campaign and divides it by the total office expense of the campaign.
B) A metric that takes the total new sales dollars generated by a campaign and divides it by the total fixed cost of the campaign.
C) A metric that takes the total new sales dollars generated by a campaign and divides it by the total variable cost of the campaign.
D) A metric that takes the total new sales dollars generated by a campaign and divides it by the total supplies expenses for the campaign.
E) A metric that takes the total new sales dollars generated by a campaign and divides it by the total cost of the campaign.