Disc Type Flywheel

Why is the rim type of flywheel used over the disc type of flywheel?
The ratio of maximum fluctuation of speed to the mean speed is called
The difference the maximum and minimum speeds during a cycle is called
A flywheel connected to a punching machine has to supply energy of 160 Nm while running at a mean angular speed of 12rad/s. If the total fluctuation of speed is not exceeded to ±1.75%, the mass moment of inertia of the flywheel in kgm2 is