Answer :
39.52 l
1) Since we have the following relationship
1 gallon ------------3.8 liters
2) Then we can use it to find how many liters Chris bought:
1 gallon ------------3.8 liters
10.4 ----------- x
x= 3.8 * 10.4
x = 39.52 L
Notice that we cross multiplied since it is a proportion.
3) Hence, the answer is 39.52