Washington - How do you pay for an estimated $5.8 trillion tax cut?
For President Donald Trump and Republican congressional leaders, that is the mostly unanswered $5 800 000 000 000 question.
The plan they released on Wednesday took a first step toward outlining how Republicans propose to cover some of the monumental cost over the next 10 years, mainly by removing certain tax breaks. But even those proposed changes were left vague - and wouldn't remotely pay the full cost of the tax cut.
The administration says it would eliminate most personal tax breaks. Possibly gone would be people's ability to deduct state and local taxes as well as eligible medical expenses. But doing so would still leave the tax cut more than $2 trillion shy of paying for itself.
The Trump administration argues that it can accelerate the economy's growth far beyond its current pace and, in doing so, generate enough federal revenue to cover the shortfall. Most economists have called that wishful thinking.
That's why analysts say the government would have to help pay for the tax cut by slashing programmes that serve the middle class. Or it would be forced to run the national debt up to dangerous levels, likely driving up borrowing rates for consumers and businesses.
Because the administration has put off a full accounting of the trade-offs it's prepared to make, the politically perilous decisions are being left for the tax-writing committees in the House and Senate to turn the blueprint into an actual bill.
Inevitably, analysts say, any tax-cut plan produces losers.
"You can't have responsible tax reform and everyone wins," said Marc Goldwein, senior policy director for the Committee for a Responsible Federal Budget.
The tax cut is being proposed at a time when the publicly held national debt is already $14.6 trillion. Even if tax rates for companies and families were unchanged, the debt is expected to balloon by an additional $10 trillion over the next decade.
That increase largely reflects the rising costs of Social Security and Medicare as the vast generation of baby boomers continues to retire.
The proposed tax cuts in the Trump plan would total $5.8 trillion over 10 years, according to an analysis by the Committee for Responsible Federal Budget and other reports.
That figure includes the effects of reducing the number of individual tax brackets and shrinking the corporate tax rate to 20% from 35%, among other changes.
The plan does list a few changes to generate additional revenue. But these ideas could undermine some of Trump's claims that the middle class as a whole would benefit from the changes.
For example, families could no longer reduce their taxable income with personal exemptions for dependents in their household. This would return about $1.6 trillion to the government. It could also nullify the benefits Trump says would result from doubling the standard deduction people now receive if they don't itemize their taxes.
Losing the personal exemption means some middle class families might end up paying more in taxes, said Ernie Tedeschi, a former Treasury Department adviser who is a policy economist at the investment bank Evercore ISI.
"For the average family, they don't have enough details yet" [to know whether the plan helps them], Tedeschi said.