How to start for this problem?

Three machines X, y, Z with capacities proportional to 2: 3 : 4 are producing bullets. The probability that the machines produce defective bullets are 0.1, 0.2 and 0.1 respectively. A bullet is taken from a day's production and found to be defective.What is the probability that it came from machine X ? Identify the most likely machine that has produced it.