Pixar Animation Studios has released 24 feature films. Due to time constraints due to final examination week, there is only time for a movie marathon consisting of 4 Pixar films. (a) How many ways can you watch 4 Pixar movies in a row, accounting for possible multiple viewings? (b) How many ways can you watch 4 Pixar movies in a row, without watching any one film more than once? (c) How many ways can you watch any group of 4 Pixar movies? (d) What is the probability of watching four different Pixar movies if two of them are Ratatouille and The Incredibles?