SQL Query to Linq (Group By and Sum)

SQL:

Select C.sName as CustomerName,  S.sName as Salesperson,

      Sum(O.nQty) as Qty, Sum(O.mAmount) as Amount
From tOrders  O
      Inner Join tCustomer C On C.CustomerID = O.CustomerID
      Inner Join tSalesperson S On S.SalespersonID = O.SalespersonID

Group By C.sName,  S.sName

 LINQ:

var query = from order in db.Orders
                group order by new { Customer = order.Customer,
SalesPerson = order.SalesPerson }
                    into grp
                    select new
                    {
                        Customer = grp.Key.Customer.Name,
                        SalesPerson = grp.Key.SalesPerson.Name,
                        Quantity = grp.Sum(o => o.Quantity),
                        Amount = grp.Sum(o => o.Amount)
                    };