6. In a certain Statistics class of a certain college, it is known that a student will pass with 3 chance. The class is composed of 15 students. If a student passes or fails the class has no influence on the performance of any other student. For the random variable S15 that counts the amount of passes in the class, calculate the following: (a) (b) What is the probability that all students fail the class? What is the probability that at least two students will pass? Hint: Use a suitable property.