Palmer Co. had a deferred tax liability balance due to a temporary difference at the beginning of 2012 related to $800,000 of excess depreciation. In December of 2012, a new income tax act is signed into law that lowers the corporate rate from 40% to 35%, effective January 1, 2014. If taxable amounts related to the temporary difference are scheduled to be reversed by $400,000 for both 2013 and 2014, Palmer should increase or decrease deferred tax liability by what amount?

a. Decrease by $40,000

b. Decrease by $20,000

c. Increase by $20,000

d. Increase by $40,000

Why decrease by 20000 rather than increase?