What is the $4-$period Mean Absolute Deviation $($MAD$)$ calculated at the end of period $6$ while using the exponential smoothing model forecast information that is shown? For your calculation convenience, a portion of the table is provided below.

$\backslash$table$[[$Period$,$Demand,$\backslash$table$[[$Exponential Smoothing Forecast$],[)=(0\mathrm{.}20$ for this Period$]]],[1,107,-],[2,110,106\mathrm{.}00],[3,113,110\mathrm{.}00],[4,106,108\mathrm{.}20],[5,109,107\mathrm{.}00],[6,112,108\mathrm{.}81]]$

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