7, i'm pretty sure, hope I helped!
I believe the problem is just simply asking for us to convert the value from one unit to the other. This case from m^3 to km^3. From the SI units, we know 1 km is equal to 1000 m. We do as follows:
118 m^3 ( 1 km / 1000 m )^3 = 1.18 x 10^-7 km^3
The answer is C. 146g because you add all of the masses of the individual elements and then mulyiply by 1.72 to get your answer.
The metric system is based on powers of 10 so it is much easier to convert units, often just by moving the decimal point.
