Over hanging bricks problem (Medium level)

Four bricks. each Of length l, are put on the top of one another in such a wav that part of each extends beyond the one beneath. The largest equilibrium
extensions are
(a) Top brick over hanging the one below by L/2
(b) Second brick from top over hanging the one
below L/4
(c) Third brick from top overhanging by bottom one by L/6
(d) The total overhanging length on the edge of the
bottom brick is 11L/12