Its 1000 Rs. ( 800 cash + 200 goods), Its so simple - he got 1000 fake- gave 1000 fake -got 1000 orignal- gave 800 original and 200 goods to the lady, kept 200 original with him. Now he returned 1000 original ( net refund out of his own 1000-200 = 800). Total Loss is his own cash 800+goods 200 = 1000. THANKS GOD SHOPKEEPER DID NOT HAVE ANY FAKE NOTE, ELSE IT WOULD HAVE MORE CONFUSING CROSS HAND TRANSACTION.