The Sweet Smell Fertilizer Company markets bags of manure labeled "not less than 60 lb dry weight." The packaged manure is a combination of compost and sewage wastes. To provide good-quality fertilizer, each bag should contain at least 30 lb of compost but no more than 40 lb of sewage. Each pound of compost costs Sweet Smell 5ϕ and each pound of sewage costs 4ϕ.
Use a graphical LP method to determine the least-cost blend of compost and sewage in each bag.