Answer: $E[Y_t] = 0.6$;

**Explanation:** For an ARMA(1,1) model: $Y_t = c + \phi Y_{t-1} + \theta \epsilon_{t-1} + \epsilon_t$ Given: $Y_t = 0.3 + 0.5Y_{t-1} - 0.6\epsilon_{t-1} + \epsilon_t$ Where: - $c = 0.3$ - $\phi = 0.5$ - $\theta = -0.6$ The long-run mean (unconditional mean) for an ARMA(1,1) model is: $$E[Y_t] = \frac{c}{1 - \phi} = \frac{0.3}{1 - 0.5} = \frac{0.3}{0.5} = 0.6$$ Therefore, the long-run mean is $E[Y_t] = 0.6$.

Author: LeetQuiz Editorial Team