Given three vectors a = 2i + 3j + 4k, b = i - 2j + k, and c = i + j - k. For a vector r satisfying r × a = b and r · c = 3, the value of |r| 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: