Use R to answer these questions and type the code. 1. Suppose there are twenty multiple choice questions in an economic class quiz. Each question has four possible answers, and only one of them is correct. Find the probability of having six or less correct answers if a student attempts to answer every question at random. 2. If there are ten cars crossing a bridge per minute on average, find the probability of having thirteen or more cars crossing the bridge in a particular minute. 3. First set the seed of 10. Then select ten random numbers between five and nine 4. Suppose the mean checkout time of a supermarket cashier is five minutes. Find the probability of a customer checkout being completed by the cashier in less than three minutes. 5. Assume that the test scores of a college entrance exam fits a normal distribution. Furthermore, the mean test score is 85, and the standard deviation is 9.2. What is the percentage of students scoring 90 or more in the exam?