What is the probability that you will get exactly zero
heads? What is the probability that you will get exactly one head? What is the probability that you will get exactly 4 head? If it helps, there are <span><span><span><span>2 to the </span><span>4th power... </span></span> </span><span>24</span></span>
possibilities for the sequence of four flips. Try writing them all out and see if you can spot a pattern.