Marginal costing-contribution

NIKHITHA (Student) (133 Points)

13 September 2014  
Can you please explain the meaning of this line? "The contribution concept is based on the theory that the profit and fixed expenses of a business is a " JOINT COST " which cannot be equitably apportioned to different segments of the business. " How can the profit and expenses be treated as joint cost?why can't they be equitably apportioned?