You are the technical consultant for an action-adventurefilm in which a stunt calls for the hero to drop off a 20.0-m-tallbuilding and land on the ground safely at a final vertical speedof 4.00 m/s. At the edge of the buildingís roof, there is a 100.-kgdrum that is wound with a sufficiently long rope (of negligible mass) has a radius of 0.500 m,and is free to rotate about itscylindrical axis with a momentof inertia I0. The script calls for the 50.0-kg stuntman to tiethe rope around his waist andwalk off the roof.

a.
Determine an expressionfor the stuntmanís linearacceleration in terms of hismass m, the drumís radius r,and moment of inertia I.
b.
Determine the required value of the stuntmanís accelerationif he is to land safely at a speed of 4.00 m/s, and use this valueto calculate the moment of inertia of the drum about its axis.

Now for a I obtained the following relationship: a= (mgr^2) /(I - mr^2) . Now the issue with this expression is that its also in terms of g. But I'm not sure how else to change it.
And for part b, since the rope is negligible in mass is it fair to assume that the drum is a disk -> so I=1/2mr^2?