Implement the Money Model.

Tasks:

• Money is amount and currency.
• Add the behaviour needed to sum two Money instances.
• Add the behaviour needed to multiply a Money to a factor.
• Add the behaviour needed to convert Money to a different currency given a Date (the Date of the conversion rate).
• Finally, given a list of Items, where each Item has a Price in ARS and a Tax, it is necessary to calculate the sum of all the Items (Price * Tax) and then convert the total to Dollars with the conversion rate of the previous Date.