2. If the null space of an 8 x 7 matrix is 5-dimensional, what is the dimension of the column space? 3. If a 6 x 8 matrix has four pivot columns, what is the dimension of its null space Is the column space R4? Why or why not? 4. If A is a 3x7 matrix, what is the smallest possible dimension of Nul A? Is it possible that the transformation x Hy Ax is one-to-one?