What steps are use in first entry

Q4. Record the following transactions in the books of Sahdev & Sons assuming all transactions have been entered within the state of Bihar, Charging CGST and SGST @ 9% each.
(i) Bought goods from Nanak Bros. for ₹4,00,000 at 10% trade discount and 3% cash discount. 25% of the amount paid at the time of purchase.

Firstly we will less 10 % trade discount.
Secondly we will calculate the amount of GST applicable in it.
In third step we will calculate the amount (%) paid in cash then we will calculate the amount of discount on cash paid.
After that we can pass the entey
Purchases a/c Dr.
Input CGST a\c Dr.
Input SGST a/c Dr.
To cash a/c
To discount rec. A/c
To Nanak bros a/c

Amount of cash discount will be calculated not on cash paid but on 25% of purchase price minus gst