function    value=Vprod(B)
%  multiplication V*B
B=sparse(B);
n1=size(B,1);
m=size(B,2);
n=n1+1;
y=-1/sqrt(n);
x=-1/(n+sqrt(n));
sm=sparse(sum(B));
value=sparse( [ y*sm
                x*(ones(n1,1)*sm)] );
value=sparse(value+sparse( [  zeros(1,m)
                              B          ]) );
