We do expect you to remember that 0 encodes black, 255 encodes white, and grey levels are in between. We do not expect you
to know or remember what happens out of this range. But we do expect you to be able to figure this out based on examples, as
those given in that exam.
So, the values in the matrix A are computed modulo 256. So these are the values you are used to, thus you should be able to
deduce that the matrix A corresponds to the right hand side image. Thus B must be the left image. And we see that the 6 pixels
in the lower right side are all black. Therefore values greater than 255 must be displayed as black (namely 0).
Now Gil says this is not what he gets when implementing such examples. This may well be implementation dependent. But given
the example in the exam, black (namely 0) is the only reasonable possibility.