4 Section 2.5. Page 88

 4.1 problem 1
 4.2 problem 3
 4.3 problem 4
 4.4 problem 5
 4.5 problem 6
 4.6 problem 7
 4.7 problem 9
 4.8 problem 10
 4.9 problem 11
 4.10 problem 12
 4.11 problem 13