soporific

Oh-kay, you guys. I need the bright ones among you to help me with my homework. -wink, wink, nudge, nudge Games-

In the U.S., 10% of teenage girls have iron deficiency. Suppose 2 adolescent girls are chosen at random. Find the probability that
a) both girls have iron deficiency
b) one girl has iron deficiency and the other one does not

I have some possible answers but don't want to confuse you. Please help a porn friend out. -=eyelash flutters=-