the revenue function is given by r(x)=x times p(x) dollars, where x is the number of units sold and p(x) is the unit price. if p(x) 27(3)^-x/7

The number if marbles of different colors stored in a hat is listed below: 4 red marbles 10 green marbles 7 blue marbles. without looking in the hat, dan takes out a marble at random. he replaces the marble and then takes out another marble from the hat. what is the probability that dan takes out a blue marble in both draws?