To pursue her goal of being a business owner, Mary left a job that paid $40,000 per year. At the end of her first year in business, her cash revenues summed to $90,000, and her explicit costs were $50,000. Also, in order to fund her business startup, Mary cashed in a $20,000 certificate of deposit that was providing a yield of 5%. Ceteris paribus, Mary's economic profit is: