[tex-k] typo in The METAFONTbook

[胡亚捷 (Hu Yajie)]

The answer to exercise 17.2 in the MFbook (page 247) has bad spacing.
Knuth forgot to "turn off" the space factor after the question marks:

mfbook.tex, lines 9118--20:
\answer The save instruction gives `?' a fresh meaning, hence `?' is
a numeric variable unconnected to any other variables. When the group
ends and `?' is restored to its old meaning, the value of the group

The answer to exercise 19.1 (page 250) has the same problem, if you
look closely enough. (By the way, the last sentence of the same answer
is illogical: it essentially says that it's wise to put A before B
because A belongs before C. I hope it can be reconsidered.)