Why do you have to know each testing tools?​

A200-mm wide strip 25 mm thick is fed through a rolling mill w/two powered rolls each of radius = 250 mm. the work thickness is to be reduced to 22 mm in one pass at a roll speed of 60 rev/min. the average flow stress of the work material, as it passes through the rolls is 175 mpa. the friction coefficient between rolls and work material is 0.20. 1, determine a)-if friction is sufficient for rolling.b)- if friction is sufficient: c)- calculate roll force i calculate roll torque. d)- calculate roll power.