Ignoring the small elastic region, the true stress $(\sigma)-\operatorname{true}$ strain $(\varepsilon)$ variation of a material beyond yielding follows the equation $\sigma=400 \varepsilon^{0.3} \mathrm{MPa}$. The engineering ultimate tensile strength value of this material is ____________ $\text{MPa}$.
(Rounded off to one decimal place)
