I''m doing question 27QP of Corporate Finance (10th by Ross). I have 2 questions:

1. Chegg online solution was wrong in calculating incremental CF => wrong NPV. Can you help me get the right final number?

2. Why use NPV instead of Profitability Index? How do I know which case I use what?

Calculating Incremental Cash Flows Darin Clay, the CFO of MakeMoney.com, has to decide between the following two projects: Year Project Million Project Billion $1,200 +160 lo 400 960 200 200 600 The expected rate of return for either of the two projects is 12 percent. What is the range of initial investment (Io) for which Project Billion is more financially attractive than Project Million