please answer in excel with steps!!!

4. Suppose you are bearish on Amazon stock, and its market price is $100 per share. You tell your broker to sell short 1,000 shares. The margin requirement is 50%. a. What will be the rate of return If the price of Amazon declines to $70 per share? b. If the short position maintenance margin is 40%, how far can the stock price rise before the investor gets a margin call