Answer:
Given : X misses 11% of the bugs and Y misses 13%.
To Find : a)What is the probability (as a %) that a randomly chosen bug will be missed by both QA checkers
b)If the program contains 1,000 bugs, what number of bugs can be expected to be missed?
Solution:
Probability of missing bugs by QA X = 11% = 0.11
Probability of missing bugs by QA Y = 13% = 0.13
So,the probability that a randomly chosen bug will be missed by both QA checkers =

Now we are given that there are 1000 bugs
No. of Bugs can be expected to be missed =

=

So, 15 bugs can be expected to be missed