Alex Burg, a cash-basis taxpayer, earned an annual salary of $80,000 at Ace Corp. in 2012, but elected to take only $50,000. Ace, which was financially able to pay Burg’s full salary, credited the unpaid balance of $30,000 to Burg’s account on the corporate books in 2012, and actually paid this $30,000 to Burg on January 30, 2013. How much of the salary is taxable to Burg in 2012?