SQL Server aggregate performance

I am wondering whether SQL Server knows to 'cache' if you like aggregates while in a query, if they are used again.

For example,

Select Sum(Field),
       Sum(Field) / 12
From   Table

Would SQL Server know that it has already calculated the Sum function on the first field and then just divide it by 12 for the second? Or would it run the Sum function again then divide it by 12?

Thanks