(CNN) At what age do children wonder whether Santa really exists?

President Donald Trump would like to know.

In a Christmas Eve call, Trump asked a 7-year-old named Collman Lloyd whether the child still believes in Santa Claus.

"Are you still a believer in Santa? Because at 7, it's marginal, right?" Trump asked Collman.

Collman's response, though inaudible to the press, left Trump with a chuckle and a smile.

The call came around 6:30 p.m. Monday as the President and first lady Melania Trump spoke on separate phones to children whose calls to NORAD had been patched through to the White House lines.

The Trumps answer calls from people to the NORAD Santa tracker phone line Monday at the White House.

In front of a crackling fire and between two Christmas trees, Trump wished Collman a Merry Christmas and asked the child's age and Christmas plans and wondered how school was going.

"Well, honey, happy Christmas, and you just take care of yourself and say hello to your family, OK? Say hello to everybody," Trump said.

The Post and Courier identified Trump's 7-year-old caller as a girl from South Carolina -- one who had never heard the word "marginal" before.

Collman told the paper she still believed in Santa, just as she told the President, and received a doll on Christmas morning.

A video from Collman's side of the Christmas Eve exchange showed she said "Yes, sir" when Trump asked if she still believed in Santa, and that she repeated, "Yes, sir" when Trump said. "At 7, it's marginal, right?"

"I was like, 'Wow.' I was shocked," she told the paper of their exchange. "It wasn't really (nerve-wracking), I just had to think of what the truth was."

In another phone call, Trump took a child's belief in Santa as a given.

"What's Santa going to get you for Christmas?" he asked, according to pool reports. "Have a great Christmas, and I'll talk to you again, OK?"

Melania Trump said on Twitter that helping children track Santa "is becoming one of my favorite traditions!" The couple participated in phone calls last year as well.

Helping children across the country track #Santa is becoming one of my favorite traditions! @Potus and I enjoyed working with @NORADSanta - #ChristmasEve pic.twitter.com/CYNkARbFaI — Melania Trump (@FLOTUS) December 25, 2018

NORAD, the North American Aerospace Defense Command, has made a tradition of using its radar system to track Santa on his trip around the globe every Christmas Eve.

The tradition, which began with a phone line mix-up in 1955, continued this year despite the ongoing government shutdown

CORRECTION: This story has been updated to reflect the proper spelling of Collman Lloyd's name.