It's worth watching all of Rep. Katie Porter's questioning.
PORTER: You don't know the cost to mail a postcard?
DEJOY: I don't ... I'll submit that I know very little about postage stamps.
...
PORTER: I'm concerned about your understanding of this agency.
With some very simple questions, Rep. Katie Porter proved the postmaster general’s poor understanding of the USPS and the detrimental changes he implemented