) Richard has just been given a multiple choice test with 10 questions. Each question has 4 possible answers. Richard hasn't been to any of the classes or done any homework and thus has no idea what the correct answer is for any of the questions. So he guesses randomly on each question, not knowing if he guess correctly or incorrectly. (Hint: Consider whether or not this is a binomial experiment.)

a) What is the probability that he will answer exactly 7 questions correctly?

b) Suppose you want to know the probability that he will answer no more than 6 questions correctly. Write down what you need to do to get the answer without actually calculating it.