Consider an unending sequence of independent trials, where each trial is equally likely to result in any

Question:

Consider an unending sequence of independent trials, where each trial is equally likely to result in any of the outcomes 1, 2, or 3. Given that outcome 3 is the last of the three outcomes to occur, find the conditional probability that
(a) The first trial results in outcome 1;
(b) The first two trials both result in outcome 1.