(S1-S2)/O=T
(S1-S2)/O=T T=1 becomes precondition to support the price of option on the stock market. You must see profits of option so that you need to pay attention to (S1-S2)/O. Please let me introduce thid equation. S1=S2+O*T is transformed equation to help you to understand (S1-S2)/O=T.