Using the data below, what is the $3$ period moving average forecast for the $4$ th week?

Week

Time Series Value

$1$

$5\mathrm{.}00$

$2$

$23\mathrm{.}00$

$18\mathrm{.}00$

$4$

$10\mathrm{.}00$

Answer format: Number: Round to: $1$ decimal places.