EF left or right join

see the query

var answer = (from c in db.customers
              join p in db.purchases
              on c.ID = p.CustomerID into subs
              from sub in subs.DefaultIfEmpty()
              group sub by new { c.ID, c.Name } into gr
              select new {
                  gr.Key.ID,
                  gr.Key.Name,
                  Total = gr.Count(x => x != null),
                  CountCompleted = gr.Count(x => x != null && x.CompletedTransaction)
              }).ToList();

the above join is left or right join?

i got the above join hint from these url

https://stackoverflow.com/a/8055893/6188148
https://stackoverflow.com/a/46947013/6188148

how to determine what kind of join is it ?

thanks