Answer:
0.02 or 2%
Step-by-step explanation:
The probability that test A is negative if the illegal drug has been used (P(A|N)) is 0.1 while the probability that test B is negative if the illegal drug has been used (P(B|N)) is 0.2.
Therefore, the probability that neither test is positive if the illegal drug has been used is:
There is a 0.02 or 2% probability that neither test is positive if the illegal drug has been used.