a=80;
b=25e6;
c=2493;
d=2500;
e=0.01;
[X1,X2]=meshgrid(0:100:50000,0:100:50000);
L=a-b./((c+X1).*(d+X2))-e.*(X1+X2);
x1=[0:100:50000]';
x2=[0:100:50000]';
r1=0.02*ones(21,1);
r2=1e-4*ones(21,1);  % 1e-4 (e nao zero) para aparecer na figura
cs=contour(x1,x2,L,[0 5 10 15 18]);...
xlabel('X1');...
ylabel('X2');...
clabel(cs);...
hold on;...
%plot(x1(1:21),r2,'b:');...
%plot(r1,x2(1:21),'b:');...
%plot(x1(1:21),x2(1:21),'b:');...
%figure(gcf);...
%hold off;
% cinvert
