Lyon, a cash basis taxpayer, died on January 15 of the current year. During the current year, the estate executor made the required periodic distribution of $9,000 from estate income to Lyon's sole heir. The following information pertains to the estate's income and disbursements for the year. For the current calendar year, what was the estate's distributable net income (DNI)?

Estate Income:
$20,000 Taxable interest
$10,000 Net long-term capital gains allocable to corpus
Estate Disbursements:
$5,000 Administrative expenses attributable to taxable income

For the current taxable calendar year, what was the estate's distributable net income (DNI)?
a. $15,000
b. $25,000
c. $30,000
d. $20,000