P = 'Calvin is a pterodactyl.'
        Q = 'Calvin is in school.'
        R = 'Calvin is Spaceman Spiff.'
        S = 'Hobbes is asleep.'
        T = 'Calvin has been transmogrified'

       I.   Translate the following into English.

           A.   (~Q -> ~R)

           B.   (Q & R) -> S

           C.   S -> (P v R)

           D.   S <-> T

      II.   Symbolize the following.

           A.   If Hobbes is not asleep, then Calvin is a pterodactyl.

           B.   Calvin is Spaceman Spiff only if he is in school.

           C.   If Calvin is a pterodactyl, then he has been
                transmogrified, and he is not Spaceman Spiff.