I don't understand these two questions

About 10% of the population of birds will show a positive result to a test for a certain stomach bacteria. Of the birds that test positive, only 96% actually have the bacteria. Of the birds that test negative, only 0.5% actually have the bacteria. What is the probability that a bird that tests negative actually has the bacteria? 0 0.85 0.0045 0 0.45 0.0085B A S If one of the 15 equally likely outcomes in the sample space S is randomly selected, find P(BIA). D . 15 O O