Exercise 5. We have the following two results from Chapter 10. Properties of options. (1) American put-call parity. The American put and call options (strike K, maturity T ) on the non-dividend-paying stock with initial price S0satisfy the following double inequality S0K C P S0KerT (2) For non-dividend-paying stock, an American call is never optimally exercised before the expiration date. In this case, C = c. Suppose now: the price of a non-dividend-paying stock is $19 and the price of a 3-month European put option with a strike price of $20 is $3, the risk-free rate of interest is 10% per annum. Consider an American put option on the same underlying and with the same maturity and strike. Determine an interval that the value of this American put option must lie.