Determine if the vectors a = [-1, 5, 3], b = [-2, 4, 7], and c = [10, 7, 1] are coplanar. Given a = [4, 7, 1] and b = [-3,1, 5]: a) Calculate the angle between a and b. b) If c = [3, -4, t], find t so that a and c are perpendicular