In the additive and$/$or multiplicative time series model with a clear indication of trend,

seasonality, and random noise $-$ what process would you undertake before proceeding

with further analysis and why:

$,$

a$)$ Filtering $$ to determine the stationary process.

b$)$ Inversion $$ to determine constant state process.

c$)$ Difference Equations $$ to determine the initial conditions.

d$)$ Trend decomposition $$ to analyze long$-$term movement.

e$)$ All of the above