HW3 (due 2/19)
 Section 3.1
 9, 24, 30, 32, 40

 Section 3.2
 15, 24

 Section 3.3
 12, 17, 24, 26

 Section 3.4
 10, 18, 26

 Section 3.5
 21, 22

 Section 3.6
 3, 8, 15, 21