Al performs an experiment comprising a series of independent trials. On each trial, he simultaneously flips a set of three fair coins. 

(a) Given that Al has just had a trial with 3 tails, what is the probability that both of the next two trials will also have this result? 

(b) Whenever all three coins land on the same side in any given trial, Al calls the trial a success. Find the PMF for K, the number of trials up to, but not including, the second success. (Hint. Negative binomial distribution)