A bag contains three dice, two of which are somewhat unusual: die A is a regular die whose faces show 1,2,3,4,5 and 6. Die B has a 4 on all 6 sides, and the faces of die C are2,2,4,4,6and 6. Suppose that a die is randomly selected, rolled, and comes up a 4. If the same die is rerolled, what is the probability that it is again a 4?