4. Yizhang and Cheryl were waiting for Prof. Stoyanov to come for a meeting. Yizhang proposed a bet. He said that he would toss a fair coin 100 times, and if it landed tails more than 60 times, he would give Cheryl $5, otherwise Cheryl would give him $5...but Cheryl didnt want to do this. She was not sure that the coin was fair, and proposed the following test - Yizhang would toss the coin 30 times, and she would see how many times the coin landed tails, and then decide. (a) How many times would you expect the coin to land tails in 30 tosses? (b) If the coin lands tails 10 times. should Cheryl play? (Figure out the probability that the coin will land tails ten times, if the coin is fair.)