The rates of on-time flights for commercial jets are continuously tracked by the U.S. Department of Transportation. Recently, Southwest Air had the best rate with 80 % of its flights arriving on time. A test is conducted by randomly selectingSouthwest flights and observing whether they arrive on time.

(a)Find the probability that exactlyflights arrivelate.

(b)Would it be unusual for Southwest to haveflights arrive late?

(Enter YES or NO)