Answer
The mass of the white gas (fuel) adds $4.354$ lb to her load.
Work Step by Step
First we must convert the units of $L$ into units of $cm^{3}$ because we will use the density of the white gas (i.e. 0.79 g/cm^3) to determine the mass of the gas.
$ {2.5 L}\times\frac{1000 cm^{3}}{1 L} = 2500 cm^{3}$. Now we can take our unit of volume and multiply it by the density of the fuel; $2500 cm^{3} \times 0.79 \frac{g}{cm^{3}} = 1975 g$. Lastly we must convert the units of g into lb because the question asks for the mass in pounds; $1975 g\times\frac{1 lb}{453.592 g}= 4.354 lb$
