Let X be an n x k matrix, and let y be an n x 1 vector. Select all of the following statements which must be true. If n = k, then there does not exist any k x 1 vector b which solves the equation...

Extracted text: Let X be an n x k matrix, and let y be an n x 1 vector. Select all of the following statements which must be true. If n = k, then there does not exist any k x 1 vector b which solves the equation X™Xb=X™y. O If XTX has rank k, then there is a unique k x 1 vector b which solves the equation XTXb=XTy. If n > k, then there is a unique k x 1 vector b which solves the equation XTXb=X"y. O If X has rank n, then there is a unique k x 1 vector b which solves the equation XTX6=XTy. There is a uniquek x 1 vector b which solves the equation XTX6=XTy.