Write a query to display the 'rate' of slab whose from_unit is 2001 and to_unit is 4500.

Assuming you are using SQL, here is a step-by-step guide on how to write the query:

1. Start by specifying the action you want to perform. In this case, you want to select data, so you start your query with the SELECT keyword.

2. Specify the column you want to display. In this case, you want to display the 'rate', so you add rate after the SELECT keyword.

3. Specify the table where the data is stored. You do this with the FROM keyword. In this case, let's assume the table is called 'slab', so you add FROM slab after SELECT rate.

4. Specify the conditions for the data you want to select. You do this with the WHERE keyword. In this case, you want the 'from_unit' to be 2001 and the 'to_unit' to be 4500, so you add WHERE from_unit = 2001 AND to_unit = 4500 after FROM slab.

So, your final query should look like this:

SELECT rate 
FROM slab 
WHERE from_unit = 2001 AND to_unit = 4500;

This query will display the 'rate' of the slab whose 'from_unit' is 2001 and 'to_unit' is 4500.