Hossein would like his colleague Stefan to develop a moving average forecast with nine periods, but he knows that Stefan is familiar only with single exponential smoothing as a forecasting technique. In the interest of expediency, Hossein decides to tell Stefan to create a single exponential smoothing forecast that has the same effect as a moving average. What alpha should Hossein tell Stefan to use to approximate a moving average forecast with $\frac{\text{I}}{2}=9?$

a$.0\mathrm{.}20$

b$.0\mathrm{.}30$

c$.0\mathrm{.}15$

d$.0\mathrm{.}25$