Matt is a resident of Nevada who performs services in California and Nevada. He sells his tax and accounting practice for $500,000 of goodwill. There is no covenant not to compete. The sales price is based on the prior year's gross income, of which $400,000 was from California clients and $100,000 was from clients outside of California. What percentage of the sales price is taxable on Matt's California income tax return? A. 10% B. 20% C. 50% D. 80%