27.1 problem 11
27.2 problem 12
27.3 problem 13
27.4 problem 14
27.5 problem 15
27.6 problem 16
27.7 problem 17
27.8 problem 18
27.9 problem 19
27.10 problem 20
27.11 problem 21
27.12 problem 22
27.13 problem 23
27.14 problem 24
27.15 problem 25
27.16 problem 26
27.17 problem 27
27.18 problem 28
27.19 problem 29
27.20 problem 30
27.21 problem 31
27.22 problem 32
27.23 problem 33
27.24 problem 34
27.25 problem 35
27.26 problem 36
27.27 problem 37
27.28 problem 38
27.29 problem 39
27.30 problem 40
27.31 problem 41
27.32 problem 42
27.33 problem 43
27.34 problem 44
27.35 problem 45
27.36 problem 46
27.37 problem 47
27.38 problem 48
27.39 problem 49
27.40 problem 50
27.41 problem 51
27.42 problem 52
27.43 problem 53
27.44 problem 54
27.45 problem 55
27.46 problem 56
27.47 problem 57
27.48 problem 58
27.49 problem 59
27.50 problem 60