Reverse charge payment on gstr-3b

Dear Sir,

My question is how to make payment  of GST on purchases (where RCM applies)?

The details are given in the below example..

Suppose I  have purchases of Rs.500000 from unregistered dealers (so 5% RCM applies) and another Rs.500000 from registered dealers (where I can claim input 5%) in July.

My total sales for July are Rs.1200000 (5% GST Rate)

In the above situation what is my GST liability for July and how to file the Return GSTR 3B before 20th of this month ?

Kindly reply sir...

Thanks in Advance..

Swamy