Hi can somebody explain this problem. I know the solution but I don't understand. Denver Company, a calendar-year corporation, had the following actual income before income tax expense and estimated effective annual income tax rates for the first three quarters in 2008:

Quarter Income Before Income Tax Exp Estimated Effective Annual Tax Rate at the end of each Qr

1 100,000 30%

2 140,000 24%

3 180,000 30%

Denver's income tax expense in its interim income statement for the third quarter should be:

A.$126,000.

B.$68,400.

C.$62,400.

D.$54,000.