Air pollutants common in U.S. cities include fine particulate matter (PM) and ozone (O3). PM is measured as "inhalable" particles 10 micrometers in diameter or "fine inhalable" particles 2.5 micrometers in diameter. Suppose that studies show, for a particular region, that cities exceed PM2.5 standards 20% of the time and exceed ozone standards 10% of the time. Assume that PM2.5 and ozone measurements are statistically independent.

A) Determine the probability that a city, selected at random, exceeds one of the standards.

B) If a city exceeds the standards, what is the probability that it exceeds only the PM2.5 standard?