Given the demand and forecast values shown in the table below,

$\backslash$table$[[$Period$,$Demand,Forecast$],[$June$,495,484],[$July$,515,506],[$August$,519,528],[$September$,496,506],[$October$,557,550]]$

the forecast error for September is

$10\mathrm{.}00.$

$1\mathrm{.}00.$

$39\mathrm{.}00$

$-10\mathrm{.}00$