10% of engines manufactured on an assembly line are defective. If engines are randomly selected one at a time and tested, what is the probability that the first defective engine will be found between the 5th trial and the 25th trial, inclusive?
The Attempt at a Solution
I believe this is just a binomial distribution with Bin(n,1) where n varies between 5 and 25.
This is way off because I am getting 6.47...
thanks ahead of time.