The F22 in the image is about 7 diagonal pixels long, that is √2⋅7 pixels length. The ship in the picture is 1727 pixels long, which equates to an actual length of almost exactly 3300m.
As a bonus this allows us to calculate the barrel-diameter: At 14 pixels width, this indicates a 27m diameter or a barrel-strength of a bit over 12m. Not sure if that is enough to contain the nuclear explosion that is mean to be fired inside it…
I had a professor who in the last lecture gave us the list of all the questions he had (something like 170) and from which he would pick some subset.
He had genuinely managed to ask about pretty much everything in the course, so this really was more of a check-list of knowledge that we were supposed to have. As such it was really nice!