4. for each of the following pairs of vectors v1 = (x1, y1) and v2 = (x2, y2) in (a)–(e), carry out the following steps: (i) the lines through v1 and v2 generate a grid (of parallelograms) on the xy-plane. sketch v1, v2, and this grid. (ii) find the area of one of the parallelgrams by computing the determinant of the matrix x1 x2 y1 y2 . is this matrix invertible? (iii) determine whether {v1, v2} is a basis of r 2 .