MP test for an exponential rate

Let $X_1,X_2,…,X_n$ be a random sample from an $\mathrm{Exp}(\lambda)$ distribution, where $\lambda\in\{1,2\}$. For testing $H_0:\lambda=1$ against $H_1:\lambda=2$, the most powerful test of size $\alpha$, $\alpha\in(0,1)$, will reject $H_0$ if and only if