Preview [6 points total, 3 points each] Suppose a fair coin is flipped 1000 times. Let the random variable X, take the value O if the ith flip is heads and 1 if the ith flip is tails. Let X = _- Xi. a) Find E(X), and use your answer, combined with Markov's inequality, to find an upper bound on the probability that the number of tails is at least 700. b) The variance of X is 250 (you don't need to prove this). Use this fact and Chebyshev's inequality to find an improved upper bound on the probability that the number of tails is at least 700. File