In between two plates that fix the ends in place, a hollow aluminum bar is placed. The outer dinmeter of the bar is $50mm$ and the liner diameter of the bar is $40mm,$ The total length of the bor is $?$ meter. $600mm$ from the left side, a vertical bar is attached at point is $($see figure$),$ forces are appled at the to the ends of the vertical bar.

a$)$ What is the maximum possible force that can be applied if the max shear stress in the rod is $50$ MPa? $($Round to the nearest ten$)$

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