White Corporation estimates that its 2018 taxable income will be $800,000 and its tax liability will be $272,000. For each of the following independent cases, compute the minimum quarterly estimated-tax payments that will be required to avoid an underpayment penalty.

a. White Corporation's 2017 tax return showed taxable income of $700,000 and a tax liability of $238,000.

b. White Corporation's 2017 tax return showed a net loss and $0 tax liability for the year.