Let A, B, C and D be the following matrices:
a) For each matrix in the list above, figure out whether the matrix is invertible, then enter in "invertible" or "not invertible".
b) For each matrix in the list above, enter in "point" if the output grid covers a point, "line" if the output grid covers a line, "plane" if the output grid covers a plane, and "3-space" if it covers all of three-dimensional space.