8.1 problem 199
8.2 problem 200
8.3 problem 201
8.4 problem 202
8.5 problem 203
8.6 problem 204
8.7 problem 205
8.8 problem 206
8.9 problem 207
8.10 problem 208
8.11 problem 209
8.12 problem 210
8.13 problem 211
8.14 problem 212
8.15 problem 213
8.16 problem 214
8.17 problem 215
8.18 problem 216
8.19 problem 217
8.20 problem 218
8.21 problem 219