3. (4+5 points.) Suppose Bob throws a dart at a circular board of radius R. The dart board can be represented by the set C' 2 {(16, y) : 11:2 + y2 S R}. Suppose the probability of landing the dart in any subset A of the board is given by the fraction of board area lying in A. (a) What is the probability that the dart hits exactly the centre? What is the prob ability that the dart lies between a distance a, and b from the centre where a