Statistical Inference — size of a test, parametric pmf

Let X be a random variable with pmf $P(x)=\frac{3+2\theta+\mu}{15}$ at $x=1$, $\frac{5+\theta-2\mu}{15}$ at $x=2$, $\frac{7-3\theta+\mu}{15}$ at $x=3$, where $\theta\ge0,\mu\ge0$ are unknown constants and $\theta+\mu\le2$. For testing $H_0:\theta+\mu=1$ versus $H_1:\theta=\mu=0$, the null hypothesis is rejected if $x=2$ or 3. The size of the test based on a single observation is: