A punching machine carries out 5 holes per minute. Each hole of 30 mm dia in 40 mm thick plate requires 10 NM of energy per mm^2 of the sheared area. The punch has a stroke of 90 mm. find the power of the motor required if the mean speed of the flywheel if 20 m/s. If the total fluctuation of speed is not to exceed 2% of the mean speed. Determine the mass of the flywheel?