6. You flip a fair coin 36 times. Let $36 denote the number of heads resulting from the 36 tosses. Now you want to calculate P(S36 = 19) by using the following two methods. (a) If you use the binomial coefficient () with some integers n and k, what is the exact expression (or number) of the probability? (b) If you use the central limit theorem and approximate the probability as P(18.5