How can I have discount on a kit?

I have a kit item C

the kit item C is BOM and  combined of item A and item B

the selling price of item C is 1000

the selling price of A is 400

the selling price of B is 300

Go to sales order and create an order for item C

book the order

and the system will create another two lines for item A and item B

I need to apply discount 10 % on item C

5 % on item A

3 % on item B

How can I do that