For a given group data group simple exponential smoothing is being used to forecast demand. The previous forecast of $110$ turned out to be four units more than actual demand. The next forecast is $109\mathrm{.}2,$ implying a smoothing constant, alpha, equal to:

$0\mathrm{.}10$

$0\mathrm{.}20$

$0\mathrm{.}60$

$0\mathrm{.}15$