A vector \(\vec a\) is parallel to the line of intersection of the plane determined by the vectors \(\hat i, \hat i + \hat j\) and the plane determined by the vectors \(\hat i - \hat j, \hat i + \hat k\). The obtuse angle between \(\vec a\) and the vector \(\vec b = \hat i - 2\hat j + 2\hat k\) is
(A) \(\frac{3\pi}{4}\)
(B) \(\frac{2\pi}{3}\)
(C) \(\frac{4\pi}{5}\)
(D) \(\frac{5\pi}{6}\)