There are 7 special subjects at Ichiro's school: art, music, gym, library,
enrichment, typing, and research. Students only take 1 special subject
each school day. A special subject is not taken more than once a week.
Assume that special subjects are assigned randomly.
Ichiro has library on Monday. If the remaining subjects during the school week
are assigned randomly from the other 6 subjects, what is the probability that he
has art on Friday?