How to get sum of data in a list using multiple column values

I have a list using this Linq query

filterEntities = (from list in filterEntities where list.Id== 0 && list.Id== 1 && list.Id == 3 && list.Id== 6 select list).OrderBy(r => r.Id).ToList();
 

Now this linq returns a list like

ID  Age
 0    18
 0    19
 1    21
 3    24
 6    32
 6    08
 

I want to generate a list using sum of same Id's which returns like

ID  Age
 0    37
 1    21
 3    24
 6    40
 

Please suggest me possible query

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