A recent survey indicated that 80% of American COVID-19 patients only had mild symptoms. Suppose 4 American COVID-19 patients were selected at random. a. What is the probability that all 4 only had mild symptoms? b. What is the probability that exactly 3 had mild symptoms? c. What is the probability that at least 1 had mild symptoms? d. Suppose that in a sample of 4 COVID-19 patients, 3 of them had been hospitalized (i.e., only 1had mild symptoms). Is there any evidence to suggest mild symptom rate is lower than 80%? Explain