Please explain how to calculate deferred tax liability! Answer is not 21000!

Grand Corporation reported pretax book income of $600,000. Tax depreciation exceeded book depreciation by $400,000. In addition, the company received $300,000 of tax-exempt municipal bond interest. The company's prior- year tax return showed taxable income of $50,000. Compute the company's current and deferred income tax expense or benefit. (Leave no answer blank. Enter N/A or zero.) N/A $ Current income tax Deferred income tax expense