Dan's Danimal Palace needs your help $($yet again$).$ Dan is currently planning for the future and production of his wonderful cat hammocks but is unprepared for how many he needs to make. Determine the upcoming demand for Summer $2021$ for cat hammocks by using a $3-$season moving average. Round to the nearest unit of demand. Prior realized demand is in the table below:

$\backslash$table$[[$Year$,$Season,Demand$],[2019,$Spring,$189],[2019,$Summer,$172],[2019,$Fall,$150],[2019,$Winter,$417],[2020,$Spring,$664],[2020,$Summer,$380],[2020,$Fall,$521],[2020,$Winter,$179],[2021,$Spring,$669],[2021,$Summer $???,]]$