French phrase
Si j'en prends ~, quel prix ?
Meaning
If I buy ___, how much will it be?
When to use it
Used to ask the price for a specified quantity. It refers to an item already under discussion.
Example dialogue
Si j'en prends un kilo, quel prix ?
If I buy one kilo, how much will it be?
Le kilo est à 8 euros, donc 8 euros.
It's 8 euros a kilo, so 8 euros.