answer chapter 8, question 3.1
answer chapter 8, question 3.2
answer chapter 8, question 3.3
answer chapter 8, question 3.4
answer chapter 8, question 3.5
answer chapter 8, question 3.6
answer chapter 8, question 3.7
answer chapter 8, question 3.8
answer chapter 8, question 3.9
answer chapter 8, question 3.10
answer chapter 8, question 3.11
answer chapter 8, question 4
add question 5
answer chapter 8, question 5
add question 6
answer chapter 8, question 6
add question 7
answer chapter 8, question 7
add question 8
answer chapter 8, question 8