A fair coin is flipped 3 times. The toss results are recorded on separate slips of paper (writing "H" if Heads and "T" if Tails), and the 3 slips of paper are thrown into a hat.
a) Find the probability that all 3 tosses landed Heads given that at least 2 were Heads.
b) Two of the slips of paper are randomly drawn from the hat and both show the letter H. Given this information, what is the probability that all 3 tosses landed Heads?