I drew 4 plots of a mathematical equation in my mathematica notebook, but I need to combine thses 4 plots in to a single graph showing all four.

I use the syntax - Show[{fig1,fig2,fig3,fig4}, PlotRange-> Automatic] but I'm unable to combine them into one.

i'm returned with this output - show::gcomb: "Could not combine the graphics objects in Show[{fig1,fig2,fig3,fig4},PlotRange->Automatic]"

and I get this error- Coordinate Skeleton[328] should be a pair of numbers, or a Scaled or Offset form.

I'm attaching my notebook file for your references, kindly check it out and help me as soon as possible.

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