CBS Evening News anchor Norah O’Donnell confronted Independent Vermont Senator and Democratic presidential candidate Bernie Sanders over the cost of his ambitious agenda, and was astonished when Sanders told her “nobody knows” what his programs will cost.

On Friday night’s edition of the CBS Evening News, O’Donnell played portions of a recorded interview, including one section in which she introduced Sanders as a “self-proclaimed Socialist,” to which Sanders corrected “Democratic, put in there please!”

“Your agenda has promised free healthcare for everybody, free college tuition, and to pay off people’s college loans,” O’Donnell said, and asked “The price tag for that is estimated to be $60 trillion dollars over 10 years, correct?”

“Well look, we have political opponents who come up…” Sanders began.

“You don’t know how much your plan costs?” O’Donnell interrupted.

“You don’t know, nobody knows, this is impossible,” Sanders said, as O’Donnell cut him off again.

“You’re going to propose a plan to the American people and you’re not going to tell them how much it costs?” O’Donnell said.

“Of course I will,” Sanders said, then added “You know exactly what healthcare costs will be, one minute, in the next 10 years if we do nothing. It will be a lot more expensive than a Medicare for All single-payer system.”

O’Donnell did not broadcast any follow-up to this exchange.

A CNN analysis of Sanders’ agenda was published this week, and estimated a price tag of $60 trillion in additional spending, but that estimate did not include costs for many of Sanders’ proposals.

Watch the clip above via CBS News.

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