splot 无法正确绘制图形

Question

这个方程必须绘制点 $(0,0)$，因为当 $x= 0 时，y=0$。但无论我如何排列这个方程，它都不会绘制点 $(0,0)$。有人能帮我解决这个问题吗？

    \pdfpagewidth 85mm      % DIN-A4: 210mm
\pdfpageheight 65mm     % DIN-A4: 297mm
\voffset = -70pt        % Vertical Offset
\hoffset = -170pt       % Horizontal Offset


\begin{center}
\begin{minipage}[t]{\pdfpagewidth} 
\begin{tikzpicture}[>=latex,x=1pt, y=1pt] 


\begin{axis}[   
    axis lines=center,
    xtick={0,10,20,30,40,50,60}, 
    ytick={0,20,40,60,80,100,120}, 
    xlabel=\footnotesize{$I$},         
    ylabel=\empty,     
    ticklabel style = {font=\scriptsize},
    xlabel style={below right}, 
    ylabel style={left},  
    %%HIER DEFINIERST DU DIE DIMENSION DER ACHSEN
    xmin=-1,                %% cm
    xmax=65,                %% cm
    ymin=-1,                %% cm
    ymax=125,                %% cm
    %axis equal image
]

  \addplot +[no markers,
      raw gnuplot,
      line width = 0.7pt,
      black
      
      ] gnuplot {
         set xrange [0:100];
    set yrange [0:120];
    set view 0,0;
      set contour base;
      set cntrparam levels discrete 5;
      unset surface;
      set view map;
      set isosamples 500;
      set samples 500;
      splot y-(x*(50-x)*((0.32*exp(x))/(1.2+1.901885*exp(x)-x**3)));
    };
\end{axis}
\end{tikzpicture}
\end{minipage}
\end{center}