Which Machine Made the Defect?

A parts factory runs exactly two machines, and every part comes from one of them.

• Machine A makes $60\%$ of the day's parts, and $2\%$ of what it makes is defective.
• Machine B makes the remaining $40\%$, and $5\%$ of what it makes is defective.

One part is drawn at random from the day's combined output and it turns out to be defective.

What is the probability that this defective part came from Machine B?