Let $\mathrm{S}(\alpha)=\left\{(\mathrm{x}, \mathrm{y}): \mathrm{y}^2 \leq \mathrm{x}, 0 \leq \mathrm{x} \leq \alpha\right\}$ and $\mathrm{A}(\alpha)$ is area of the region $\mathrm{S}(\alpha)$. If for a $\lambda, 0<\lambda<4, \mathrm{~A}(\lambda): \mathrm{A}(4)=2: 5$, then $\lambda$ equals
