The probability that the bulb is good is 12/15.
Since we have taken 1 item out the remaining total is now 14, so the probability of getting a defective bulb is now 3/14.
Now you multiply the probabilities together to get (12/15)(3/14)=(4/5)(3/14)=12/70=6/35
In 5 years, the price increased about 30%.
I am not good at perentages, so correct me if I'm wrong. Also this is an estimation, not the exact percentage.
