When n liters of fuel was added to a tank that was already ~$\frac{1}{3}$~  full, the tank was filled to  ~$\frac{7}{9}$~ of its capacity.  In terms of n, what is the capacity of the tank, in liters?

~$\frac{10}{9}$~n

~$\frac{4}{3}$~n

~$\frac{3}{2}$~n

~$\frac{9}{4}$~n

~$\frac{7}{3}$~n