When you look at stock market, you can enjoy the price of option by equation. The stock market is supported by option relative to the price of goods. (B-S)/T=O is basic of Bond and stock. Bond is public sight to take part in stock market. (B-S)/T=O can tell you the relation between Bond and Stock. (S-S)/T=O can become index to make up for profits in the trend of option as one of stock. T must be used for (S-S)/S=T and (O-O)/O=T.