A trader writes five naked put option contracts, with each contract being on 100 shares. The option price is $15, the time to maturity is six months, and the strike price is $96.

(a) What is the margin requirement if the stock price is $87?

(b) How would the answer to (a) change if the rules for index options applied?

(c) How would the answer to (a) change if the stock price were $105?

(d) How would the answer to (a) change if the trader is buying instead of selling the options?