For the parabola x2=20y, let R be a point on the curve with ordinate k2, where k>0.
(i) Determine the abscissa(s) of R in terms of k.
(ii) Obtain a formula for the distance of R from the focus of the parabola, expressed in terms of k.
(iii) If this distance equals 13, find the corresponding value(s) of k.