5. Calculating return on investment. Which of the following would offer the best return on invest transaction ment? Assume that you buy $5,000 in stock in all three cases, and ignore interest and costs in all your calculations. Buy a stock at $60 without margin, and sell it a year later at $90. b. Buy a stock at $20 with 50 percent margin, and sell it a year later at $30. Buy a stock at $40 with 75 percent margin, and sell it a year later at $55. a. C