A steel bar 20 mm in diameter simply-supported at its ends over a total span of 40 cm carries a load at its centre. If the maximum stress induced in the bar is limited to N/mm2, the bending strain energy stored in the bar, is___________________?
(A) 411 N mm
(B) 511 N mm=
(C) 611 N mm
(D) 711 N mm

