The probability of two independent events is the product of the probability of each event. Then calculate the probabilities of each event and multiply them. Probability that the piston chosen from Machine 1 is unsatisfactory is 177 out of (177 + 413 ) = 177 / (590) = 0.3. Probability that the piston chosen from Machine 2 is satisfactory = 350 / (350 + 150 ) = 350 / 500 = 0.7. Then the joint probability is 0.3 * 0.7 = 0.21. Answer: 0.21