Compute the interest rate for the following investments:

1. A U.S. Treasury bill which matures in 92 days with a quoted price of $97.50 per $100 maturity value.
2. A share of common stock purchased one year ago at a price of $42 per share and just sold for $48. No dividends were received.
3. A share of common stock purchased one year ago for $21 and sold yesterday for $18 after receipt of a dividend check for $1.
4. A share of common stock purchased for $30 three years ago and just sold for $30. Dividends of $2.10 were received at the end of each of the three years of ownership.