Confidence interval for a triangular scale

Let $X$ be a single sample from a continuous distribution with probability density function $$f(x;\theta)=\begin{cases}\dfrac{2(\theta-x)}{\theta^2}& \text{if }0<x<\theta,\ 0& \text{otherwise,}\end{cases}$$ where $\theta>0$ is an unknown parameter. For $0<\alpha<0.05$, a $100(1-\alpha)\%$ confidence interval for $\theta$ based on $X$ is