(5 marks.) Consider the real inner product space M23 (R) (Le. the space of 2 x 2 matrices with real entries), with inner product >=Tr((: m: 52)) (a) Find an orthonormal basis for the subspace U of M12 (R) spanned by 1 U U 1 1 1 "' 1 U I (b) Find the best approximation to the matrix M = (1 3 2) in the subspace U