plot eff vs F for lucky drift

clc;
W1 = 0.5;
e = 1.6*10^-19;
Ea = 2.3;
Er = 0.04; 
Eg = 2; 
Ei = 0.55; 
F = 0:150; 
lambda_el = 0.6; 
lambda_ie = 6 * lambda_el; 
theta_c = pi/2;
alpha = 0;
for m=0:5000
    for ku=0:5000
        Ea = (kl*e*F*lambda_el*cos_theta)+(ku*e*F*lambda_el*cos_theta_star)-(m*Er);  
        cos_theta = (1 + cos(theta_c))/2;             
        cos_theta_star = (cos(theta_c)-1)/2;            
        x = ((k*(1-W1))^ku)* exp(-k*(1-W1))/ factorial(ku);          
        y = ((k*lambda_el/lambda_ie)^m)*exp(-k*lambda_el/lambda_ie)/factorial(m);          
        k = kl + ku;
        l_k = lambda_el*(kl*cos_theta) + (ku*cos_theta_star);              
        alpha = alpha + ((x*y)/l_k);
    end
end
disp("Alpha")
disp(alpha)
d = 10;
eff = exp(d*alpha);
disp("Efficiency")
disp(eff)
disp("F")
disp(F)
disp("kl")
disp(kl)
figure
plot(F,eff)

[Jan]

This is the code. What is your question?

[the cyclist]

The variable kl is not defined before it is used. Is that the problem?