lestion 5 (12 marks) :termine if the following sets are subspaces of the real vector space M23 of 2 x 2 matrices. the set is a subspace, you must use the subspace theorem to prove it. If the set is not bspace, then you must provide an explicit counterexample. a) The set S of all matrices A such that AD = DA, where D = [ g i ]. b) The set M of all matrices of the form [ 3 ll) 3 2:12 ] where s, t E R. c) The set W of all matrices of the form [ 3 f2 l where r 6 IR