In order to keep up with the demand for its new earphones, a manufacturer h ad to purchase a key p art from three different suppliers. Supplier l provides 15% of the parts and l 0% are defective. Supplier 2 provides 60% of the parts and 4% are defective. Supplier 3 provides 25% of the parts and 8% are defective.
(a) What percentage of the parts received by the earphone manufacturer are defective?
(b) Suppose the earphone manufacturer randomly selects one of her parts and finds that it is defective. What is the probability it came from Supplier l ?