“…We have chosen the parameters a and b in such a way as to build four functions (curves) which are able to reach four different points on the top side of the model (in the points (1, 0.25), (1, 0.5), (1, 0.75) and respectively (1, 1)) and three curves with points on the right side ((0.75, 1), (0.5, 1) and respectively (0.25, 1)). Based on the observation of Pugna et al (2016)’ regarding the overlapping of the curves in the neighborhood of the origin (0,0), we have changed the equation to prevent this from happening.…”