Speaking with columnist Andrew Ross Sorkin at The New York Times DealBook Conference on Wednesday, Gates, the Microsoft co-founder and philanthropist whose fortune totals over $100 billion, said that he had paid over $10 billion in taxes and that it would be “fine” if he had to pay $20 billion.

“But, you know, when you say I should pay $100 billion, OK, then I’m starting to do a little math about what I have left over,” he added. “Sorry, I’m just kidding. So you really want the incentive system to be there, and you can go a long ways without threatening that.”

Sorkin then asked Gates if he had ever spoken about this with Warren — he said he had not — and asked Gates if he would want to.

“You know, I’m not sure how open-minded she is or that she’d even be willing to sit down with somebody, you know, who has large amounts of money,” Gates said.

Warren responded with a tweet Wednesday evening.

“I’m always happy to meet with people, even if we have different views,” she said, tagging Gates directly. “If we get the chance, I’d love to explain exactly how much you’d pay under my wealth tax. (I promise it’s not $100 billion.)”

For Warren, who has made battling corporate greed and corruption a central theme of her campaign and is now among the top contenders in the Democratic primary field, attacks from Wall Street and public clashes with billionaires have been welcomed as signs of her populist credibility and reformatory zeal.

Her proposals include a 2% tax on household net worth over $50 million. She outlined a plan last week to pay for “Medicare for All,” which calls for $20.5 trillion in new federal spending over a decade, by increasing her proposed wealth tax on net worth above $1 billion to 6% annually and raising taxes on investment gains for the top 1% of households.

This week, former Vice President Joe Biden, the other top-polling contender for the Democratic presidential nomination, unleashed a new line of attacks against Warren, seeking to paint her as an elitist who believes people lack wisdom or courage unless they agree with her.

Warren’s team has been critical of Biden’s reliance on high-dollar fundraising events.

The two candidates are on opposite sides of a party divide that pits the structural changes favored by more left-leaning front-runners like Warren and Sen. Bernie Sanders, D-Vt., against a more moderate approach that speaks to values of unity and bipartisanship, which Biden espouses.

Gates, a Harvard dropout, is a chairman of the Bill and Melinda Gates Foundation, the world’s largest charitable organization. The foundation has directed billions of dollars annually toward efforts to combat malaria, reduce poverty and improve education.

Gates has expressed worries about President Donald Trump’s foreign aid policies and his style of communication.

He has also spoken in defiance of federal regulation before. In 1998, Gates testified in Congress to defend Microsoft when lawmakers questioned whether the company was abusing its market power. He argued that technological progress could happen “if innovation is not restricted by government.”

That appearance was mirrored by the congressional testimony last month of another tech industry titan, Mark Zuckerberg, chief executive of Facebook. Zuckerberg, who struck a more conciliatory tone in front of Congress than Gates did, has criticized Warren’s plan to break up tech giants.

Warren has also clashed publicly with billionaire Leon Cooperman, a hedge fund manager who wrote an open letter to the senator last month. He disagreed with Warren’s critique of the finance industry and predicted stock market losses if she were to win the presidency.

As with Gates, Warren responded with a tweet.

“Leon is wrong,” she said. “I’m fighting for big changes like universal child care, investing in public schools, and free public college. We can do all of that with a #TwoCentWealthTax. Leon can and should pitch in more — so that every kid has the same opportunities he did to succeed.”

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