sql query count and parameter in linq

in this sql query 

ALTER procedure [dbo].[spstdinfo]
@year_p int
as
select Catg_type.Catg_type,Program_type.Prog_name ,Year_info.year,
COUNT(Std_info.catg_id) as total_students from Std_info 
inner join Catg_type on Std_info.Catg_id=Catg_type.Catg_id
INNER join Program_type on Std_info.Prog_id=Program_type.Prog_id
inner join Year_info on Std_info.year_id=Year_info.year_id
where @year_p=Year_info.year
group by Catg_type,Program_type.Prog_name,Year_info.year

i try this linq query

 var re = (from  stdtable in a.Std_info
                            join catg in a.Catg_type on stdtable.Catg_id equals catg.Catg_id
                            join prog in a.Program_type on stdtable.Prog_id equals prog.Prog_id
                            join yea  in a.Year_info on stdtable.year_id equals yea.year_id
                           select new {  Std_info = stdtable, Catg_type = catg,Program_type=prog,Year_info=yea });

now how i use count and parameter year_p in linq