Suppose you flip three coins. Let X be the number of times you flip heads.

(a) List all possible arrangements of heads and tails. For example, if you flip heads twice and then tails, then type HHT. Separate each item in your list with a comma. .

(b) List the possible values that X may take, separated by commas. .

(c) What is the probability that X = 2?

(d) What is the probability of flipping tails three times?