On February 15, 2016, Brent filed his 2015 income tax return (due April 15, 2016), and he paid a tax of \(\$ 15,000\) at that time. On June 10, 2017, he filed an amended 2015 return showing an additional \(\$ 3,000\) of tax which was then paid. In 2018, Brent found that he should claim a refund of \(\$ 6,000\) because he failed to take some deductions to which he was entitled. What amount can he recover if he files the claim for refund on March 14, 2019? What if he files the claim on May 15, 2019?