Offer volume discount when some products contain number of other products(are bundle of other products)

We have two sets of products. For example, Product A belongs to the first set and then Product 2 is a bundle of 5 of Product A, while Product C is a bundle of 3 of Product A. We'd like to offer a volume discount say 10% discount if customers buy 8 of Product A. We want the discount to be automatically computed and applied to the customer's cart if you purchase both Products B and C as well.