Consider the following vectors in R³: Let W be the subspace spanned by v1 = [1, 2, 3] and v2 = [2, 1, -1]. Find a linearly independent set of vectors that spans W, so that neither v1 nor v2 is a scalar multiple of any of them.
a) [1, 2, 3] and [1, 0, 1]
b) [1, 2, 3] and [0, 1, 1]
c) [2, 1, -1] and [0, 1, 1]
d) [1, 2, 3] and [1, 1, 1]