// @author Frank M. Carrano, Timothy M. Henry
// @version 5.0
StockLedger myStocks = new StockLedger();
myStocks.buy(20, 45);                   // Buy  20 shares at $45
myStocks.buy(20, 75);                   // Buy  20 shares at $75
double capGain = myStocks.sell(30, 65); // Sell 30 shares at $65