Trading account Original Accounting Rules ( Help me)

For an example ,Mrs Lakshmi Lal Jain was a Small trader , she asked me to prepare the trading account she gives the following details of items regarding her trade details


1. opening stock 15 lakh
2. purchases. 3.5 lakh
3. sales. 20 lakh

only these three items details available from her books

QUERY:

1. now having with these three items how to find out the closing stock and gross profit??? I need formula explanation


2. actually gross profit is how it is calculated in this scenario how we can find out gross profit and closing stock also


Help me