please help me answer 6,7,8,10

6. Explain, using one of the principles of finance, why some people choose to invest in speculative, risky options that expose investors to a great deal of risk and others invest in U.S. Treasury bonds. 7. A firm trading on the New York Stock Exchange just posted extraordinary earnings (income) after its controller implemented a new method of depreciation. Its stock price does not increase at all. Which principle of finance best explains this phenomenon? 8. Provide your own example why interest rates reflect opportunity cost. 9. Provide an argument for why one of the principles of finance from chapter 1 is most important and why? 10. Martha plans to graduate as a nurse next year and has begun planning her future with her financial planner. She forecasts her annual income to be $50,000 a year for the next 20 years, and plans to spend approximately $38,000 annually. After working hard during those years and completing her MBA, she plans to significantly increase her annual income in the subsequent 20 years. She expects to earn $90,000 a year in her managerial role. The financial planner informs her that the real risk-free interest rate over the next forty years is expected to be 5% annually. a. Use the lifetime budget constraint to determine her maximum annual expenditures beginning in twenty years? b. How is the answer in part a) impacted if the interest rate is 10% ? c. How does your answer change if she reduces her spending in the first twenty years to $30,000 ? d. What is the opportunity cost of the annual $8,000 of additional expenditures in part a)