Simple exponential smoothing is being used to forecast demand. The forecast of a given period is $66,$ which turned out to be $4$ unit less than actual demand. The next forecast is $66\mathrm{.}6.$ what is smoothing constant, alpha?

A$.0\mathrm{.}01$

B$.0\mathrm{.}10$

C$.0\mathrm{.}15$

D$.0\mathrm{.}20$

E$.0\mathrm{.}60$