Indicate whether the following temporary differences produce current or non-current deferred tax assets or deferred tax liabilities (considered independently).
a. Book depreciation in excess of tax depreciation.
b. Tax depreciation in excess of book depreciation.
c. Increase in the allowance for doubtful accounts.
d. Increase in the reserve for warranty settlements.
e. Write-down for impairment of book goodwill.
f. A current-year NOL.