13. Put Prices. How does the price of a put option respond to the following changes, other things equal? Does the put price go up or down? (LO2)

a. Stock price increases.

b. Exercise price is increased.

c. Risk-free interest rate increases.

d. Expiration date of the option is extended.

e. Volatility of the stock price falls.

f. Time passes, so the option's expiration date comes closer.