Determine whether the given set of matrices under the specified operation, matrix addition or matrix multiplication, is a group. Recall that if both A and B are both n × n matrices, then det(AB) = det(A)det(B). Also, det(In) = 1 where In is the n × n identity matrix that has 1 along the main diagonal and 0 elsewhere. Moreover, A is invertible if and only if det(A) ≠  0.     1) The set of all 3 × 3 diagonal matrices under matrix multiplication. 2) The set of all 3 × 3 upper-triangular matrices under matrix addition

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