Urgent- a mechanics rotation question

Hi I am really stuck on the following and have an exam on it in 2 days. Can somebody please help me. I have attempted it but think I have done it all wrong. (I have indicated how many marks each part of the question is worth at the side).

a. A particle of mass m moves at constant velocity v relative to a point P with a closest distance of approach a. Find the angular momentum of the particle about P.[5]

my attempt: mva, I don't think this is right as in my textbook it says to use mva if a is the closest distance of perpendicular approach which, it may not be.

b. A belt drives the circumference of a cylindrical wheel of Radius R, mass M with no slipping. The tension in the belt is T. Friction in the wheel bearing causes an effective Torque N to act on the wheel.

(i). If the velocity is constant what is T in terms of N.[5]
my attempt: Friction= T (as acceleration=0)
Therefore as N=TR, T=N/R.

(ii). The bearing is lubricated removing all significant friction and the velocity of the belt increases with uniform acceleration a. Write T in terms of M, a and R.[15]

my attempt: Force=Ma=T
This is as far as I got and I am not even sure if this is right, can somebody please explain how to do this question?