Extend Exercise P15.12 to a program that can handle shares of multiple companies. The user enters commands buy symbol quantity price and sell symbol quantity price. Hint: Keep a Map> that manages a separate queue for each stock symbol.

Data from Exercise P15.12

Suppose you buy 100 shares of a stock at $12 per share, then another 100 at $10 per share, and then sell 150 shares at $15. You have to pay taxes on the gain, but exactly what is the gain? In the United States, the FIFO rule holds: You first sell all shares of the first batch for a profit of $300, then 50 of the shares from the second batch, for a profit of $250, yielding a total profit of $550. Write a program that can make these calculations for arbitrary purchases and sales of shares in a single company. The user enters commands buy quantity price, sell quantity price (which causes the gain to be displayed), and quit. Hint: Keep a queue of objects of a class Block that contains the quantity and price of a block of shares.