About average price of the stock in holding

I have a following scenario for which I would like to know the average price of my shares.

Day 1: I brought say 500 shares @ Rs. 50/-
Lets say a week after that I feel that this share is going to be at downside today so I thought of selling my shares.
Day 7 (10:00 am) : I sold all 500 shares @ 48/-
Day 7 (3:00 pm) : I brought back all 500 shares @ 45/-
(Basically I did intraday short on Day 7)

My question is what would be avg. cost of my shares on Day 8 ?

You made a profit of 3 rs and it would be 50-3 = 47.
(you can adjust for brokerage charges)

Your average buy price for 500 shares is Rs.50/-
(No change)

It will be treated as Intraday Trade.
Here, you made Intraday Profit of Rs.1500/-

Thank you for the reply