There are 6 barrels of root beer in the store.
In the picture below it is shown how much liters of root beer is in each barrel.
2 customers come to the store and one of them bought 2 full barrels, while the other one bought 3.
It is also known that the second customer bought twice as much root beer than the first one.
There was only 1 barrel left, which one?
Need a solution to this.