Collect the monthly time series of currency in circulation in Hong Kong from publicly available source and complete the following tasks:

$($a$)$ Decompose the time series into trend, seasonality, and residuals. Please present the result as a four$-$panel chart starting with the observed data followed by the three components.

$($b$)$ Forecast currency in circulation $12$ months ahead with a $($seasonal$)$ na$$ve model, an exponential smoothing model and an ARIMA$/$SARIMA model. Please prepare a summary to explain how you determine the parameters of your chosen models.

$($c$)$ Compare the forecasting performance of the three models based on a forecast performance indicator. Please prepare a summary explaining the results.