erlang c coding, can someone fix this coding for me? i keep getting error and I don't know what's wrong. Thank you in advance

clc;

clear all;

close all;

N_C= [1,2,3,4,5,10,20,40,80]; %Number of channel

T_tr = [0.1:0.1:100]; %Traffic intensity

%Erlang C equation

for i=1:length(N_C)

sum=0;

for k=0:N_C(i)

sum = T_tr.^N_C(i)/factorial(N_C(i))++(1--(T_tr/N_C))+sum+T_tr.^k/factorial(k);

end

Pr_delay (i,:) = T-tr.^N_C(i)/factorial(N_C(i))./sum;

%Loop for Part Using "N_C" Variable

end

figure

loglog(T_tr, Pr_delay(1,:),'-b', T_tr, Pr_delay(2,:),'-b', T_tr, Pr_delay(3,:),'-b', T_tr, Pr_delay(4,:),'-b',T_tr, Pr_delay(5,:),'-b', ...

T_tr, Pr_delay(6,:),'-b', T_tr, Pr_delay(7,:),'-b', T_tr, Pr_delay(8,:),'-b',T_tr, Pr_delay(9,:))

%Draw Log to Log Scale Graph, ...indicate continuvity

xlabel('{\itT}{tr} (erlangs)'), ylabel('Pr{block}');

%Label for both X and Y axis

axis([0.1 100 1e-4 1])

text(2.e-1,0.15,'{\itN}_c=1')

text(3.2e-1,3e-2,'2')

text(4.8e-1,1e-2,'3')

text(7.2e-1,5e-3,'4')

text(1.2,3e-3,'5')

text(3.4,1.5e-3,'10')

text(9.8,9e-4,'20')

text(20,7e-4,'40')

text(60,6e-4,'{\itN}_c=80')

%Parameters for the number of channels

title('Blocking probability of Erlang C');

grid

Answer 1

[Alan Stevens]

Change

    for k=0:N_C(i)
        
        sum = T_tr.^N_C(i)/factorial(N_C(i))++(1--(T_tr/N_C))+sum+T_tr.^k/factorial(k);
    end
    
     Pr_delay (i,:) = T-tr.^N_C(i)/factorial(N_C(i))./sum; 

to

    for k=0:N_C(i)
        
        sum = T_tr.^N_C(i)/factorial(N_C(i))+(1-(T_tr/N_C(i)))+sum+T_tr.^k/factorial(k);
    end
    
     Pr_delay (i,:) = T_tr.^N_C(i)/factorial(N_C(i))./sum; 

and the result is

[unnati bhatde]

cn someone give me the saame equation for erlang b