Given ⃗ = 5 − 2 , find the expression of a unit vector ⃗ in the case under below situations. (a) ⃗ ∥ ⃗ (b) ⃗ ⊥ ⃗, if ⃗ lies in the y-plane

A) (a) ⃗ = ⃗ / ||⃗||
B) (a) ⃗ = ⃗ / 2||⃗||
C) (b) ⃗ = ⃗ / ||⃗||
D) (b) ⃗ = ⃗ / 2||⃗||