How can we infer from 'someone is taking computer cannot take psychology' that if someone is taking psychology she can't take computer?
Bunuel
The students in College X must take two, and no more, of these five subjects: computing, electronics, mechanics, architecture, and psychology. Students who take computing cannot take psychology. Students who take electronics cannot take architecture. Students who take mechanics cannot take electronics. Is Student G, a student at College X, taking psychology?
(1) Student G is taking architecture as one of her two subjects.
(2) Student G is taking neither electronics nor computing.
Five subjects: computing(c), electronics(e), mechanics(m), architecture(a), and psychology(p).
c and p cannot be together. e will not go with either of a or m.
So, possible cases/combinations: (e,c); (e,p); (a,p); (a,c); (m,c); (m,p); (a,m)
(1) Student G is taking architecture as one of her two subjects.
So, possible combinations: (a,p); (a,c); (a,m)
Insufficient as p may or may not be there.
(2) Student G is taking neither electronics nor computing.
So, possible combinations: (a,p); (m,p); (a,m)
Insufficient as p may or may not be there.
combined
(a,p) and (a,m) are possible.
Insufficient as p may or may not be there.
E