If a = i + 4j + 2k, b = 3i - 2j + 7k, and c = 2i - j + 4k, then a vector d which is parallel to vector a × b and satisfies c · d = 15 is:

If a = (0, -1, 2), b = (1, 0, -1) and c = (2, -1, 0), then which of the following is a unit vector parallel to a - b - c?

If a = 2î + 3ȷ and b = î - ȷ, then a - b is:

If vectors a and b are perpendicular with |a| = 5 and |b| = 12, then |a + b| is equal to: