Forever quilting is a company that designs and distributes quilting kits. the kits are priced at $120 each. (there is no quantity discount.) the costs of the materials that go into each kit are $45. it costs $5 in labor to assemble a kit. the company has monthly expenses of $1,000 for rent and insurance, $200 for heat and electricity, $500 for advertising in quilting magazines, and $3,500 for the monthly salary of its owner. forever quilting's marginal revenue is: