A block 'A' of mass 2m is placed on another block 'B' of mass 4m which in turn is placed on a fixed table. The two blocks have a same length 4d and they are placed as shown in fig The coefficient of friction (both static and kinetic) between the block 'B' and table is `mu`. There is no friction between the two blocks. A small object of mass m moving horizontally along a line passing through the centre of mass (cm.) of the block B and perpendicular to its face with a speed v collides elastically with the block B at a height d above the table.

(a) What is the minimum value of v(call it `v_0`) required to make the block A topple?
(b) If `v=2v_0`,find the distance (from the point P in the figure ) at which the mass m falls on the table after collision. (Ignore the role of friction during the collision).