Rhy Co. had a deferred tax liability balance due to a temporary difference at the beginning of 2007 related to $600,000 of excess depreciation. In December of 2007, a new income tax act is signed into law that lowers the corporate rate from 40% to 30%, effective January 1, 2009. If taxable amounts related to the temporary difference are scheduled to be reversed by $300,000 for both 2008 and 2009, Rhy should increase or decrease deferred tax liability by what amount?
a. Decrease by $30,000
b. Decrease by $15,000
c. Increase by $15,000
d. Increase by $30,000