P2: An exam consists of 20 truelfaise questions. John knows the correct answers to 8 of the questions and decides to choose at random the answers to the remaining questions. a Find the probability that John answers i 10 questions correctly II all the 20 questions correctly. (4 marks) A student gains 2 marks for each correct answer, has one mark subtracted for each incorrect answer, and gains no marks if the question is left unanswered. Ii Compare the expected number of marks when the student answers all the questions with the marks she will gain if she just answers the questions to which she knows the correct