HW2 (due 1/31)
 Section 2.1
 15b, 15d, 16b, 28b, 28d, 30, 32

 Section 2.2
 4, 6, 14, 15, 26, 29, 44b

 Section 2.3
 13, 14, 18, 19c, 26, 30