An investor has an option portfolio composed of 5,000 identical short call options. The call options delta is 0.4.

1. What does it mean intuitively that the delta is 0.4?
2. How can the portfolio be made delta-neutral?
3. How will the delta-neutral portfolios value change if there is a small (e.g. 0.1%) upward movement in the stock price?
4. Will the delta-neutral portfolios value change if there is a large (e.g. 10%) upward movement in the stock price? If no, why not. If yes, what hedge could protect against the change in the portfolios value?