Assertion (A): The maximum efficiency $\left ( \eta =\frac{1-\sin \phi }{1+\sin \phi } \right )$ of a screw jack is same, where 
is the friction angle, for both motion up and motion down the plane.
Reason (R): The condition for the maximum efficiency for motion up and motion down the plane is same, given by $\alpha =\frac{\pi }{4}-\frac{\phi }{2}$ where $\alpha$ helix angle.