f=5000;
C=[2.000 1.000 0.665 0.500 0.400];
Xc=[15 30 48 58 76];
%% a
data=C*10^-6*f
eq=1./data
%% b
figure
subplot(4,4,[1,2;5,6])
p=polyfit(C,Xc,2)
Cinterp = linspace(min(C),max(C));
f = polyval(p, Cinterp);
f2=p(1)*C.^2+p(2)*C+p(3)
plot(C, Xc, 'o', Cinterp, f, '--')
axis([0 2 10 80]);
legend('Experiment Data','Polynomial Fitting', 'Location','northeast')
xlabel('C(\muF)')
ylabel('XC(\Omega)')