Joey moved to California from Iowa on May 1 of the tax year. At that time, he sold his home in Iowa and rented an apartment in California. He transferred all of his savings to a California-based bank. His wages from his Iowa job were $12,000 and he earned wages of $32,000 from his California job. He earned interest during the tax year totaling $600, one-third of which was from his Iowa bank account. How much income is taxable on his California tax return?