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$),],[1,7\mathrm{.}5,],[2,8\mathrm{.}2,],[3,4\mathrm{.}0,],[4,11\mathrm{.}0,],[5,15\mathrm{.}2,],[6,12\mathrm{.}2,],[7,,]]$