Jamara has started a home party business that hosts parties and those attending paint signs. Jamara must pay $500 a year to be a representative for Paint A Sign. In addition, Jamara buys all the materials for the parties, including the metal base, the paints, brushes, stencils, and transfers. These items all add up to $10 on average. Jamara charges each participant $25 for each sign they make. For Jamara's Paint A Sign business, the gross margin or contribution margin for Jamara's business is: