Sue Bradley from Weapons System Support Center, Philadelphia, is conducting a study on forecasting demand of sonar system parts. The UICP model uses an exponential smoothing model with a smoothing constant of 0.20 to forecast quarterly demand. Unfortunately, there are several observations missing in her data base. If t represents the quarter in a 36-quarter period, A_t represents the actual or observed demand in period t, and F_t represents the forecast in period t, determine the missing observation in period 4.

t	at	ft
2	33	41.52
4		39.816
5	42	39.0528
6	36	39.64224

A) 33

B) 36

C) 39

D) 42