Gasoline-contaminated ground water from a nearby gas station has diffused underneath a house. Sticking a probe 3 meters into the floor in the basement, you find that the concentration of the hydrocarbons is $9 \times 10^{-5} \mathrm{~kg} / \mathrm{m}^{3}$. Assume the diffusion coefficient is $10^{-6} \mathrm{~m}^{2} / \mathrm{s}$ and the basement has no hydrocarbons present.

a. Calculate the flux density transported into the basement by diffusion.

b. If the basement has a floor space of $200 \mathrm{~m}^{2}$, what is total mass flux?