The Formula S_t = Wy_t + (1 −W)St−₁ Is Used

The formula S_t = wy_t + (1 −w) St−₁ is used in time-series forecasting with exponential smoothing,where S_t is the exponentially smoothed time series at time t,y_t is the value of the time series at time t,and w is the smoothing constant.The forecasted value at time t + 1 where w = .4 is given by:

A) Ft _{+ 1} = 0.4yt ₊₁ + 0.6St _{+ 1}
B) Ft _{+ 1} = 0.4y_t + 0.6S_t
C) Ft _{+ 1} = 0.4y_t + 0.6St− ₁
D) Ft _{+ 1} = 0.4yt− ₁ + 0.6S_t