3. (20 points) Consider a circular dart board with radius 1 that is inscribed in a square frame: (-1,1) (-1,-1) (1,1) (1,-1) Suppose you throw n independent darts at random into the square frame and let X equal the number of darts that land on the dart board (i.e., in the circle). We define the estimator = 4X n in terms of X. (a) Compute the expected value of , making sure to show your work. (b) What is an estimator for?