qqp question1: A warehouse has the same model of product from two different manufacturer A and B, and each product has equal chance of originating from A or B. 10% of product from A are defective, 5% of product from B are defective. What is the probability that the product is defective (select from warehouse randomly)? question2: What are two infinite nilpotent matrices A and B, for which the product AB is not nilpotent?