Assume perfect prediction, common knowledge, and $0$ interest rate. Suppose $P_{\text{S}\text{p}\text{o}\text{t}}>$

$P_{\text{f}\text{u}\text{t}\text{u}\text{r}\text{e}\text{s}}$ and any arbitrage is allowed. Explain the implication of arbitrage activity toward the

difference between $P_{\text{s}\text{p}\text{o}\text{t}}$ and $P_{\text{f}\text{u}\text{t}\text{u}\text{r}\text{e}\text{s}}$ using graphs.