Marker's comments on Test 2 (Cook):

Average mark is 28/34.

Most students did well on Question 1, and reasonably well on
Question 3.  Most students had trouble with Question 2; espcially
finding the right set of clauses to add to the CNF formula to
ensure that all new variables added to replace a single variable
all have the same truth value, and ensure that no variable occurs
more that three times in the resulting formula.  (See Solutions).