Show all formula, substitution and calculations. Round off to 2 decimals. An exam contains a total of 15 multiple-choice questions with four possible choices for each question. What is the probability...

Show all formula, substitution and calculations. Round off to 2
decimals.

An exam contains a total of 15 multiple-choice questions with four possible
choices for each question. What is the probability that a student will get:
a) No answers incorrect.
b) At least 14 questions correct.