Sir i am stuck for this question

(b) Assume that Bob is taking a quiz, which contains 6 questions. In this quiz, the first two questions are True-False questions with 2 possible answers each, only one of which is correct. The last four questions are multiple choice questions with 4 possible answers each, only one of which is correct. Now assume Bob did not study for the quiz, so he guesses independently on each question. Find the probability that Bob answers exactly 1 question correctly in this quiz. (Hint: You may introduce two random variables X and Y. X is the number of correct questions to first two True-False questions, and Y is the number of correct questions to the last four multiple choice questions.)