5) Suppose you toss a coin 4 times, with heads being a success. a) Write down explicitly all the possible sequences that would correspond to exactly 2 heads (successes) in these 4 tosses (Ex: SSFF is one sequence). How many such sequences are there in total? b) Suppose you toss a coin 25 times, with heads being a success. How many sequences of S and F are there that correspond to exactly 20 successes in these 25 tosses