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