In an assembly unit in the STEM building at the University of Ottawa, a mill, lathe, and reamer machine 30%, 45%, and 25% of parts, respectively. An inspector knows that 2%, 3% and 2% of the parts respectively machined by the milling machine, the lathe and the reamer are defective. If a defective part is chosen at random, what is the probability that it was machined by the milling machine?