#$15$

Using the data below, what is the value of RMSE?

$\backslash$table$[[$Week$,$Time Series Value,Forecast$],[1,6,],[2,3,8\mathrm{.}00],[3,5,3\mathrm{.}00],[5,8,4\mathrm{.}00]]$

Answer format: Number: Round to: $2$ decimal places.