The cross-section at mid-span of a beam at the edge of a slab is shown in the sketch. A portion of the slab is considered as the effective flange width for the beam. The grades of concrete and reinforcing steel are M25 and Fe415, respectively. The total area of reinforcing bars ($A_s$) is $4000 \: mm^2$. At the ultimate limit state, $x_u$ denotes the depth of the neutral axis from the top fibre. Treat the section as under-reinforced and flanged. $(x_u > 100 \: mm)$

The ultimate moment capacity (in kNm) of the section, as per the Limit State Method of $\text{IS } 456:2000$ is

1. $475.2$
2. $717.0$
3. $756.4$
4. $762.5$