16. A company gets graphics cards from two sources. The first source provides 40% of the cards, and the second source provides 60% of the cards. Past experience has shown that of the cards from the first source are found to be defective, while of the cards from the second source are found to be defective. If a graphics cards is selected and found to be defective, what is the probability it was provided by the first source?
(A)
(B)
(C)
(D)