Final answer:
Bob's consumer surplus is $2. Therefore, Bob is willing to pay $8 for the book.
Step-by-step explanation:
Bob's consumer surplus is the difference between what he is willing to pay for the book and the actual price he paid. In this case, Bob's consumer surplus is $2, which means he is willing to pay $2 more than the price of the book.
Therefore, the price Bob is willing to pay for the book is the actual price plus the consumer surplus, which is $6 + $2 = $8.
So, the correct answer is D) 8.