Answer:
3.08%
Step-by-step explanation:
If we choose a random disk, the probability that it is produced by manufacturer I is 36% so the probability that it is produced by manufacturer I AND is defective is 1% of 36%
Similarly,
the probability that it is produced by manufacturer II is 20% so the probability that it is produced by manufacturer II AND is defective is 7% of 20%
the probability that it is produced by manufacturer III is 44% so the probability that it is produced by manufacturer III AND is defective is 3% of 44%.
Since a disk can only be produced by one manufacturer, the probability that the disk defective is
1% of 36% + 7% of 20% + 3% of 44% =
0.01*0.36 + 0.07*0.20 + 0.03*0.44 = 0.0308 = 3.08%