2. Determine which of the following subsets are the subspaces of the given vector spaces: (i) All vectors of the form (a, b, c), with b = a + c in R. (ii) All matrices with A = AT in Mnxn (R), where Mnxn (R) is the vector space of all nx n matrices over R. (iii) All matrices of the form ( a ) ) with ad 0 in M22 (R). (iv) All matrices with det(A) = 0 in Mnxn (R). (v) All vectors of the form (a, b, c), where ab = 0, in R. (vi) Is the set W = {(a, b, c) a = b} a subspace of both R and C? : (vii) Is U a subspace of Mnxn (R) for a fix A Mnxn (R), where U={B Mnxn (R) AB = BA}?