在实体框架中用linq查询替换SQL联接和组查询

我有一个现有的SQL查询：

select 
    mn.accountid, sum(u.peak), sum(u.text), sum(u.datagig),
    sum(p.minutesallowed), sum(p.messagesallowed), sum(p.dataallowed)
from 
    usage u
inner join 
    mtn mn on u.mtnid = mn.Id
inner join 
    [plan] p on p.id = mn.planid
group by 
    mn.accountid

使用实体框架，我正在将其转换为linq，我已经走到了这一步：

var tots = from u in currentUsage
   join mn in mtns on u.mtnId equals mn.Id
   join p in plans on mn.PlanId equals p.Id
   group u by u.AccountId into g
   select new MainUsageResults
   {
       TotalPeakMinutes = g.Sum(x => x.Peak),
       TotalData = g.Sum(x => x.DataGig),
       TotalMessaging = g.Sum(x => x.Text),
       TotalAllowedMinutes = g.Sum(x =>  ???) ,
       TotalAllowedMessages = g.Sum(x =>  ???) ,
       TotalAllowedData = g.Sum(x =>  ???) 
   };

我不知道如何汇总联接表上的数据。在SQL中，联接中会有一整列可用，但这里的情况似乎并非如此。在本例中，如何获得联接表上的列的总和？