  Continuing our series of papers on the 3-D structure and accurate distances
of Planetary Nebulae (PNe), we present here the results obtained for the
planetary nebula NGC\,40. Using data from different sources and wavelengths, we
construct 3-D photoionization models and derive the physical quantitities of
the ionizing source and nebular gas. The procedure, discussed in detail in the
previous papers, consists of the use of 3-D photoionization codes constrained
by observational data to derive the three-dimensional nebular structure,
physical and chemical characteristics and ionizing star parameters of the
objects by simultaneously fitting the integrated line intensities, the density
map, the temperature map, and the observed morphologies in different emission
lines. For this particular case we combined hydrodynamical simulations with the
photoionization scheme in order to obtain self-consistent distributions of
density and velocity of the nebular material. Combining the velocity field with
the emission line cubes we also obtained the synthetic position-velocity plots
that are compared to the observations. Finally, using theoretical evolutionary
tracks of intermediate and low mass stars, we derive the mass and age of the
central star of NGC\,40 as $(0.567 \pm 0.06)$M$_{\odot}$ and $(5810 \pm
600)$yrs, respectively. The distance obtained from the fitting procedure was
$(1150 \pm 120)$pc.
