问题如下：
As explained in Chapter 12, historically calls were traded on exchanges before puts. Explain how you can synthetically create a European put from a European call. Assume no dividends are paid and no arbitrage opportunities exist.
解释：
From put-call parity:
Call + PV(K) = Put + 5
so that:
Put = Call + PV(K) - 5
The put can therefore be created by buying the call, shorting the stock, and investing PV(K) so that it grows to K at maturity.
题目中的5是s吗？这道题是在考查ps=ck求合成吗
