Let the position vectors of points A(2,−1,4) and B(−3,5,1) with respect to the origin be a and b respectively.
a. (i) Find the vectors a and b in component form.
b. (ii) Calculate the exact value of the angle ∠AOB between a and b, where O is the origin.
c. (iii) State whether the angle obtained in part (ii) is acute, right or obtuse, giving a reason based on your calculation.