A.Ef=L3/5bh3•F/Y B.Ef=(L3/4bh3)•(F/Y) C.Ef=L3/3bh3•F/Y D.Ef=L3/3bh2•F/Y
A.σf=3FL/4bh2 B.σf=2bh2/4FL C.σf=3FL/2bh2 D.σf=1FL/7bh2