figure
a=0:0.05:50;
y=50*a-a.^2;
plot(a,y)

figure
aa=0:0.05:50;
bb=0:0.05:50;
[a b]=meshgrid(aa,bb);
z=a.*b;
mesh(a,b,z)

figure
aa=0:0.05:50;
bb=0:0.05:50;
[a b]=meshgrid(aa,bb);
z=a.*b;
c=contour(a,b,z);
clabel(c)
hold on
plot(a,50-a)
