A long slender bar having uniform rectangular cross – section is acted upon by an axial compressive force. The sides B and H are parallel to x – and y – axes respectively. The ends of the bar are fixed such that they behave as pin – jointed when the bar buckles in a plane normal to x – axis, and they behave as built – in when the bar buckles in a plane normal to y – axis. If load capacity in either mode of buckling is same, the value of H/B will be
(a) 2 (b) 4 (c) 8 (d)16