Let W = 0 and y 0 . Determine whether W is a subspace of R2. : x 3y (a) W is not a subspace because it is not closed under scalar multiplication. (b) W is not a subspace because it is not closed under vector addition (c) W is not a subspace because it does not contain the zero vector. (d) Wis a subspace because it is the null space of a matrix. (e) Wis a subspace because it is a span of a set of vectors.