Sam quit a $30,000-a-year job with a local heating and air conditioning firm to go into business for himself. After his first year in business, his accountant showed him an income statement that indicated Sams firm had a profit of $40,000. During this year Sam had drawn a salary of $20,000. What was Sams accounting profit, his entrepreneurial profit, and his opportunity cost? Explain the difference between accounting and entrepreneurial profit.