Amy has a box containing 6 white, 4 red, and 8 black marbles. she picks a marble randomly. it is red. the second time, she picks a white marble. in the third attempt, amy picks a white marble again. amy has not replaced the marbles she picked. the probability that the fourth marble amy picks is black is . if amy picks a black marble in the fourth attempt, the probability that in the fifth attempt she will pick a red or a black marble