A bag contains four different cards, labeled green, red, blue and yellow. Two cards are selected at random from the bag "replacement," meaning that after the first selection is made, the selected card is returned to the bag before the second selection is made. "At random" means that all cards in the box have an equal chance of being selected.
a. Define the sample space for this experiment.
b. Is the event of choosing card green or blue on the first selection independent of choosing card green or red on the second selection? Why or why not?