What is the Absolute percent error for period $4$ when Three period moving average forecast method is used:$($Please round to $2$ decimal places for your answer$).$ Do Not convert to percentage, leave as a decimal value.

$\backslash$table$[[$Week or$,$Time series value,,$],[$X$($Time Period$),$or Y$($Sales$),,],[,,$Forecast,$],[1,7\mathrm{.}9,,],[2,9\mathrm{.}9,,],[3,6\mathrm{.}6,,],[4,11\mathrm{.}0,,],[5,15\mathrm{.}2,,],[6,12\mathrm{.}2,,],[7,,,]]$

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