Homework assignment 4, Due Monday, March 23, 2015.

Since the midterm exam is on Wednesday, March 25, no late homeworks
will be accepted after March 23, so that I can get the model solutions
to you before the midterm exam.

1. (40 points) Exercise 52 on page 328.
2. (10 points) Exercise 54 on page 329.
3. (10 points) Exercise 56 on page 329.