Well it seems you will have to check the conversions of gold per liter/gallon to kilograms. Things have different mass whereas liter/gallon is simply volume, or, 'space' if you will. A liter of feathers will weigh a lot less than a liter of gold.

Then on the 2nd point, it seems to me that you are only told how much he spent, not how much he earned. So it seems to me again that you will have to look up the price of gold during the time of which this story takes place (are you sure you are in a math class?) and then subtract the expenses to come up with the amount that Jack put into his bank account.