What is the rate of return of some common stock indexes $($what are some common indexes and how are they calculated is also a good question$)?$ For example you can use the S&P index, but there are others. How is this number important in deciding what are good and bad investments in projects? Give some references and familiarize yourself with the world of stocks and investing in stock funds. A good investment is considered to be one that returns above $7\%-$ why?