27.1 problem 766
  27.2 problem 767
  27.3 problem 768
  27.4 problem 770
  27.5 problem 771
  27.6 problem 772
  27.7 problem 773
  27.8 problem 774
  27.9 problem 775
  27.10 problem 776
  27.11 problem 777
  27.12 problem 778
  27.13 problem 779
  27.14 problem 780
  27.15 problem 781
  27.16 problem 782
  27.17 problem 783
  27.18 problem 784
  27.19 problem 785
  27.20 problem 786
  27.21 problem 787
  27.22 problem 788
  27.23 problem 789
  27.24 problem 790
  27.25 problem 791
  27.26 problem 792
  27.27 problem 793
  27.28 problem 794
  27.29 problem 795
  27.30 problem 796
  27.31 problem 797