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%%%%%% ----------------------The answer part
% a) plot the filter coefficients
rc = rc / sum(rc);
figure, plot(time,rc);
% b)plot the frequency response
freq = 1/T * osr;
Spec = 20*log10(abs(fft(rc)));
figure, plot(linspace(0, freq/2, length(Spec(1:end/2 + 1))), Spec(1:end/2 + 1))