Department of Housing and Urban Development Secretary Ben Carson raised eyebrows Tuesday when he struggled to describe basic terms related to the agency he oversees during a hearing before a congressional panel.

The former neurosurgeon, who had zero experience in housing before President Donald Trump nominated him to lead HUD in December 2016, appeared visibly flustered while answering questions about his department’s policies before the House Financial Services Committee.

Rep. Katie Porter (D-Calif.) asked Carson about services offered by the Federal Housing Administration (FHA), an agency housed under HUD, and government-sponsored enterprises (GSEs), which are financial services corporations created by Congress such as Fannie Mae and Freddie Mac.

But Carson drew several blanks.

Porter: Do you know what the interest rate curtailment schedule is at FHA and how it’s different from the GSEs? Carson: Well, we tend to try and maintain a lower interest rate at FHA ― Porter: I’m not asking you about the interest rate, sir. I’m asking you about debenture interest curtailment penalties. Carson: Explain.

An exasperated Porter then described to the HUD secretary how an agency he oversees functions, pointing out that servicing for nonperforming mortgages at FHA is triple the cost of the equivalent servicing for nonperforming loans at GSEs.

“That tripling of costs in servicing ... has the effect of reducing the credit availability to the American people,” Porter said. ”It makes the loans more expensive for the very homeowners that FHA is designed to serve.”

“So my question I’m trying to drive at here is why is FHA ― to use a term that I think we can both understand ― lousy at servicing mortgages?” she asked.

Carson responded that he hasn’t had “any discussions about that particular issue but I will look it up, find out what’s going on.”

Mortgage servicing, essentially how a bank manages the loans it makes, played a major role in last decade’s nationwide housing crisis.