Three machines produce the same parts.

Machine A produces 10% defective parts.
Machine B produces 5% defective parts.
Machine C produces 5% defective parts.

Suppose each machine produces 1/3 of the total production. A part is selected at random, and it is found to be defective. What is the probability that it was produced by machine B?
A) 19/56
B) 17/30
C) 1/2
D) 1/4