Loop is not working. My while loop is not working. output is initial values here. Can anyone help??

D=800;
d=[1 600 09 0.02 300 500;
   2 500 10 0.04 100 400;
   3 400 06 0.08 050 200];
g=1;
P1=400;
P2=300;
P3=100;
P=[P1;P2;P3];
f=1;
del_C1=.04*P1-.16*P3+2;
del_C2=.08*P2-.16*P3+4;
counter=1;
C=15900;
j=.1;
while C(counter)> C(j) && abs(f)>.00001
    if sum(del_C1,del_C2)<0 && del_C1>del_C2
        P1=P1+1;
        P2=P2;
        P3=P3-1;
        P=[P1;P2;P3];
        f=D-sum(P);
        C=d(:,2)+d(:,3).*P+d(:,4).*P.*P;
        counter=counter+1;
        j=counter;
    elseif sum(del_C1,del_C2)<0 && del_C1<del_C2
        P1=P1;
        P2=P2+1;
        P3=P3-1;
        del_C1=.04*P1-.16*P3+2;
        P=[P1;P2;P3];
        f=D-sum(P);
        C=d(:,2)+d(:,3).*P+d(:,4).*P.*P;
        counter=counter+1;
        j=counter;
    elseif sum(del_C1,del_C2)>0 && del_C1>del_C2
        P1=P1-1;
        P2=P2;
        P3=P3+1;
        P=[P1;P2;P3];
        f=D-sum(P);
        C=d(:,2)+d(:,3).*P+d(:,4).*P.*P;
        counter=counter+1;
        j=counter;
    elseif sum(del_C1,del_C2)>0 && del_C1<del_C2
        P1=P1-1;
        P2=P2;
        P3=P3+1;
        P=[P1;P2;P3];
        f=D-sum(P);
        C=d(:,2)+d(:,3).*P+d(:,4).*P.*P;
        counter=counter+1;
        j=counter;
    end
    del_C1=.04*P1-.16*P3+2;
    del_C2=.08*P2-.16*P3+4;
end
display(P,'Generated Power in MW')
display(C,'Total Cost in $')
display(counter,'Iterations numbers')