%gradient wrt u of state limit function for problem # 2
%y = gradgu(x,u)
function y = gradgu(x,u)
v(1) = 400*u(2) + 2000;
v(2) = 250*u(3) + 1000;
v(3) = 100*u(1) + 500;
v(4) = exp(0.7386 + 0.0998*u(4));
Dv_Du = [0 400 0 0
         0  0  250 0
         100 0 0 0
         0 0 0 0.0998*exp(0.7386 + 0.0998*u(4))];
gradGv(1) = -4/(x(1)*x(2)^2*v(4));
gradGv(2) = -4/(x(1)^2*x(2)*v(4));
gradGv(3) = -2*v(3)/(x(1)*x(2)*v(4))^2;
%gradGv(4) = 4*v(1)/(x(1)*x(2)^2*v(4)^2)+4*v(2)/(x(1)^2*x(2)*v(4)^2)...
%+ 2*v(3)^2/(x(1)^2*x(2)^2*v(4)^3);
gradGv(4) = (2/(x(1)*x(2)*v(4)^2))*(2*v(1)/x(2) ...
 + 2*v(2)/x(1)+v(3)^2/(x(1)*x(2)*v(4)));
gradGv = gradGv(:);
gradgu = Dv_Du'*gradGv;
y = -gradgu;