South, Inc., earns book net income before tax of $400,000 in year 1. It acquires a depreciable asset in year 1, and its first-year tax depreciation exceeds book depreciation by $50,000. In year 2, South earns $500,000 book net income before tax, and its book depreciation exceeds tax depreciation by $20,000. South records no other temporary or permanent book-tax differences. Assuming that the applicable tax rate is 21% in both years, what is South's balance in its deferred tax liability account at the end of year 2?

a. $0

b. $4,200

c. $6,300

d. $10,500