function q4leuven(a)
% function q4leuven(a)
%
% checks correctness of analytical solution of Question 4/Leuven 2005

B0=a+sqrt(a^2-a+0.5);
if a<1,
    C0=-1;
    A0=-1-sqrt(a^2-a+0.5);
elseif a>1,
    C0=1-2*a;
    A0=1-2*a-sqrt(a^2-a+0.5);
else
    fprintf('\nq4leuven: the problem is singular\n');
end
s=slap(1);
newmodel;
u=newsignal(1);
w1=newsignal(1);
w2=newsignal(1);
x=(1/(s-a))*(u+w1);
k2=h2hi([w1;w2],u,x+u,x+w1+w2);
fprintf('\nq4leuven: analytical')
tf(ss(A0,B0,C0,0))
fprintf('\nq4leuven: numerical')
tf(k2)