How can I find the transfer function of a lowpass filter using the Kaiser windowing method?

From the code given, how can I find the transfer function and the order of the numerator and denominator? I am having trouble on how to implement kaiserord and kaiser into the code.

% design parameters

wp=2000*pi;

ws=3000*pi;

f0=8000;

w0=2*pi*f0;

A=45;

% cut-off frequency

wc=0.5*(wp+ws);

% normalized cut-off frequency

wc_n=wc/(0.5*w0);

% delta cut-off frequency

del_wc=ws-wp;

% delta normalized cut-off frequency

del_wc_n=del_wc/(0.5*w0);

% beta

if(A<=21)

    beta=0;

elseif(21<A & A<50)

    beta=0.5842*(A-21)^0.4+0.07886*(A-21);

elseif(A>=50)

    beta=0.1102*(A-8.7);

end

% order

M=(A-7.95)/(2.285*pi*del_wc_n);

M=ceil(M);

% filter coefficients

b=fir1(M-1,wc_n,'low',kaiser(M,beta));

% magnitude

[H,f]=freqz(b,1,256,f0);

% magnitude spectrum

figure,plot(f,20*log10(abs(H)),'Color',line_color,'LineWidth',line_width),grid

xlabel('f [Hz]','FontSize',font_size), ylabel('20log_{10}(H(f)) [dB]','FontSize',font_size)

title('Magnitude Spectrum','FontSize',font_size)

set(gca,'FontSize',font_size)

set(gca,'XLim',[0 4000]), set(gca,'XTick',[0:500:4000],'FontSize',font_size)

set(gca,'YLim',[-120 20]), set(gca,'YTick',[-120:20:20],'FontSize',font_size)