Vector Algebra

Let \(\overrightarrow a\), \(\overrightarrow b\) and \(\overrightarrow c\) be three non-zero non-coplanar vectors. Let the position vectors of four points \(A,B,C\) and \(D\) be \(\overrightarrow a - \overrightarrow b + \overrightarrow c ,\lambda \overrightarrow a - 3\overrightarrow b + 4\overrightarrow c , - \overrightarrow a + 2\overrightarrow b - 3\overrightarrow c\) and \(2\overrightarrow a - 4\overrightarrow b + 6\overrightarrow c\) respectively. If \(\overrightarrow {AB} ,\overrightarrow {AC}\) and \(\overrightarrow {AD}\) are coplanar, then \(\lambda\) is equal to __________.