If the UN can prove how the funds would be used.

Last month, the director of the United Nations’ World Food Programme called on the world’s richest man to help solve the global hunger crisis. Taking to Twitter, David Beasley challenged Elon Musk to donate some of his wealth to the cause.

Nearly two weeks after Beasley’s remarks, the Tesla CEO responded via Twitter, writing that he’s willing to sell some of his company shares if the UN can provide evidence as to how it would use the funds to ‘solve world hunger.’

‘If WFP can describe on this Twitter thread exactly how $6B will solve world hunger, I will sell Tesla stock right now and do it,’ Musk wrote. ‘But it must be open source accounting, so the public sees precisely how the money is spent.’

Beasley responded, writing that he can assure that they have ‘the systems in place for transparency and open source accounting,’ and that Musk’s teams can ‘review and work with us to be totally confident of such.’

Musk’s response arrives just days after Tesla became the sixth company ever in the U.S. to be valued at $1 trillion, with Bloomberg’s Billionaires Index estimating Musk’s net worth to be at $288.6 billion.