An ellipse has its centre at the origin and foci at (±4,0). For every point P on the curve, PF1+PF2=12, where F1 and F2 denote the two foci.
(i) Find the values of a and c for this ellipse.
(ii) Determine b and hence derive the Cartesian equation of the ellipse in standard form.
(iii) Calculate the eccentricity of the ellipse.