coefficient, quadratic coefficient and quadratic coefficient) (Lu, Song, & Guo, 2002). In order to make it more intuitionistic, Eq. (1) was taken into Eq. (5) and Eq. (6) obtained as follows (in terms of uncoded values). The model filled Eq. (6) was made response surface and contour plots to predict the relationships between the independent variables and the dependent variables as follows: