To convert 8,400,000 m^3 to km^3, divide by 10^9:
8,400,000 m^3 / 10^9 = 0.0084 km^3
So, 8,400,000 m^3 is equal to 0.0084 km^3.
Next, divide 0.0084 km^3 by 0.012 km^3 to get the fraction:
0.0084 km^3 / 0.012 km^3 = 0.07.
The answer is 0.07 in its simplest form.