Pam runs a vegetable stall in the market building. Pam has no skills, no job experience, and no alternative employment. Entrepreneurs in the vegetable stall business earn $13,000 a year. Pam pays the rent of $500 a year, and her total revenue is $19,000 a year. She borrowed $500 at 15 percent a year to buy equipment. At the end of one year, Pam was offered $300 for her business and all its equipment. What are Pam's explicit costs, implicit costs, and economic profit? Pam's explicit costs are ____