function [ fval ] = F(t,x,u,ux,duxx)
% 
% Written by:
% -- 
% John L. Weatherwax                2005-06-15
% 
% email: wax@alum.mit.edu
% 
% Please send comments and especially bug reports to the
% above email address.
% 
%-----

fval(1) = duxx(1,1) - u(1)*ux(1) - 980*( ux(2) + d_bottom_H(x) );
fval(2) = duxx(2,2) - u(1)*ux(2) - u(2)*ux(1);