Fitting of experimental data

(*Ps={0.059,0.079,0.070,0.051,0.058,0.021}; (*in C/m2*)
Ec={280,390,370,330,260,100}; (*in kV/m*)*)

Xper={0,10,20,30,40, 50}; (*in %*)
Ps={0.027,0.079,0.070,0.051,0.058,0.021}; (*in C/m2*)
Ec={50,80,70,65,80,100}; (*in kV/m*)
FEf={65,86,85,77,76,70};(*in %*)

Psfit=Fit[{Xper,Ps}\[Transpose],{1,p,(p^2),(p^3),(p^4)},p];
Ecfit=Fit[{Xper,Ec}\[Transpose],{1,p,(p^2),(p^3),(p^4)},p];
FEfit=Fit[{Xper,FEf}\[Transpose],{1,p,(p^2),(p^3),(p^4)},p];

Psf[p_]:=Psfit;Ecf[p_]:=Ecfit;
α[p_]:=-((3(Sqrt[3]))/2)((Ecf[p])/(Psf[p]))(10^3);β[p_]:=((3(Sqrt[3]))/2)((Ecf[p])/((Psf[p])^3))(10^3);

α[p]

PolSBTN=ListPlot[{{Xper,Ps}\[Transpose],Table[{p,Psfit},{p,0,50,1}]},Joined->{False,True},PlotStyle->{Blue,{Blue,Thick}},PlotMarkers->{"●",""},AspectRatio->1/1,Frame->True,FrameStyle->Directive[Black,Thick],BaseStyle->{FontFamily->"Arial",FontSize->16},Axes->False,PlotRange->All]

EcSBTN=ListPlot[{{Xper,Ec}\[Transpose],Table[{p,Ecfit},{p,0,50,1}]},Joined->{False,True},PlotStyle->{Red,{Red,Thick}},PlotMarkers->{"●",""},PlotRange->{40,110},AspectRatio->1/1,Frame->True,FrameStyle->Directive[Black,Thick],BaseStyle->{FontFamily->"Arial",FontSize->16},Axes->False,PlotRange->All]

FESBTN=ListPlot[{{Xper,FEf}\[Transpose],Table[{p,FEfit},{p,0,50,1}]},Joined->{False,True},PlotStyle->{Black,{Black,Thick}},PlotMarkers->{"●",""},AspectRatio->1/1,Frame->True,FrameStyle->Directive[Black,Thick],BaseStyle->{FontFamily->"Arial",FontSize->16},Axes->False,PlotRange->All]

Clear[Tc,ϵo,T];Solve[(1/(2ϵo αt(Tc-T)))==eps, αt]

Tc=335.+273.;ϵo=8.85*(10^(-12));T=293.; Solve[(1/(2ϵo αt(Tc-T)))==1280., αt]

αt=123292;

f=(10^(-6));Plot[{f*α[p]},{p,0,50},PlotRange->All,PlotStyle->{{Thick,Darker[Green]},{Thick,Dashed,Blue},{Thick,Red},{Thick,Blue}},AspectRatio->1,Frame->True,FrameStyle->Directive[Black,Thick],BaseStyle->{FontSize->18,FontFamily->"Arial"}]

f=(10^(-9));Plot[{f*β[p]},{p,0,50},PlotRange->All,PlotStyle->{{Thick,Darker[Magenta]},{Thick,Dashed,Blue},{Thick,Red},{Thick,Blue}},AspectRatio->1,Frame->True,FrameStyle->Directive[Black,Thick],BaseStyle->{FontSize->18,FontFamily->"Arial"}]

ContourPlot[((x y+(x^2))/(Sqrt[(x^2)+(y^2)])),{x,-1,1},{y,-1,1},PlotPoints->100,PlotRange->All,Contours->50,ContourLines->True,ContourShading->True,FrameStyle->Thick,BaseStyle->{FontSize->18,FontFamily->"Arial"},ColorFunctionScaling->False,ColorFunction->(ColorData["Rainbow"][(#)]&)(**)]