function May2()

function y = F(lambda,b)
Amat = A(lambda);
[Q,R] = qr(Amat,0);
% y = b-Amat*inv(Amat'*Amat)*Amat'*b
%   = b - Q*R*inv((QR)'(QR))*(QR)'*b 
%   = b - Q*R*inv(R'*R)*R'*Q'*b
%   = b - Q*Q'*b
y = b - - Q*(Q'*b)