A uniform beam is to be picked up by crane cables attached at $A$
and $B$. Determine the distance $a$ from the ends of the beam to the
points where the cables should be attached if the maximum absolute
value of the bending moment in the beam is to be as small as possible. (Hint. Draw the bending-moment diagram in terms of $a, L,$ and the weight per unit length $w,$ and then equate the absolute values of the largest positive and negative bending moments obtained.)