A rectangular beam of cross$-$sectional dimensions $200mm$ width and $400mm$ deep is doubly reinforced with area of compressive steel of $156m{m}^2$ and tensile reinforcement of $400m{m}^2.$ Effective cover to the tensile and compressive reinforcement is taken as $30mm.$ Strength of concrete is $f_c^{\text{'}}=32$MPa. Calculate $k_u$ and write your inference of the possible failure mode.