#print
You can also use the "=" command to find out what
the 'current' line is.  Since the
current line is referred to as '.', do you see that
  .=
is the appropriate command to print the current line
number?  So if you go through a sequence like
  3p
  .=
the second command will print '3'.  That's not very
exciting, so why don't you edit file 'roger',
print the next to last line, and then use '.='
to find out what it is.  Don't forget to exit
from the editor with w, and then q.  Then
finish by typing "answer N" where
N is what you found, as usual.
#create roger
this is a short
file containing five lines
of which 
this line is next to last
indeed
#copyin
#user
#uncopyin
#match 4
#log
#next
15.1a 10
15.2a 5