Counting a list
 

I have a data file of three columns: one is a subject (math, art, etc.), the
second contains a code for the first student to get it right (AA, e.g.) and
the students that got it wrong (AA, e.g.). My data looks something like this,
but much longer:
A B C
Math AA AE
Sci AB none
Lit BE BA
Art BC AA, AC
Math AD AE

I want to compute the number of right and wrong for each cubject for each
student, in a sheet like this one:
Math R Math W Art R Art W.....
AA x y
AB
AC
AD
BA

What is the best way to calculate these numbers? What combination of
functions should I use for x and y? Thanks in advance.