Volume of solid region bounded by $z=4x$, $z=x^2$, $y=0$, and $y=3$ as an iterated integral 
Suppose R is the solid region bounded by the plane $z = 4x$, the surface $z = x^2$, and the planes $y = 0$ and $y = 3$. Write an iterated integral in the form below to find the volume of the solid R.
  $$\iiint\limits_Rf(x,y,x)\mathrm{d}V=\int_A^B {\int_C^D {\int_E^F\mathrm{d}z} \mathrm{d}y} \mathrm{d}x$$

I need to find the limits, I found A and C which are zeros and I could not find the rest of the limits

the volume comes out to be:
$$\int_{0}^4 \int_{0}^{3} \int_{x^2}^{4x}  1dzdydx$$
