A fish looking up through the water sees the outside world contained in a circular horizon. If the refractive index of water is $4/3$ and the fish is 12 cm below the surface, the radius of this circle in cm is\\
(1) $36\sqrt{7}$\\
(2) $36/\sqrt{7}$\\
(3) $36\sqrt{5}$\\
(4) $4\sqrt{5}$