Computing the Capital Gain in a Sale of Stock Suppose that you buy n shares of a stock or mutual fund for d dollars each. Later you sell some of these shares. If the sale price exceeds the purchase price, you have made a profit - a capital gain. On the other hand, if the sale price is lower than the purchase price, you experience a loss. We will designate a loss as a negative capital gain. Typically, the investors buy shares in a particular company or fund over a period of time. For example, suppose that last year you bought 20 shares of Presto Pizza at $45 per share. Last month, you bought 20 additional shares at $75 per share, and today you sold 30 shares at $65 per share. What is your capital gain? Well, which of your 40 shares did you actually sell ? Unfortunately, you cannot pick and choose. When computing capital gains, you must assume that you sell shares in the order in which you purchased them ( stock sales are a first-in, first-out application). So in our example, you sold the 20 shares that you bought at $45 each and 10 of the shares that you bought at $75 each. Your cost for the 30 shares is $1650. You sold them for $1950, a profit of $300. Design a way to record your investment transactions chronologically and to compute the capital gain of any stock sale