High blood pressure: The National Health and Nutrition Survey reported that 30% of adults in the US have hypertension(high blood pressure). A sample of 25 adults is studied. Let X denote the number of adults who have hypertension in the sample.

a. What is the mean number who have hypertension in a sample of 25 adults?

b. What is the probability that exactly 6 of them have hypertension?

c. What is the probability that fewer than 4 have hypertension?

d. Would it be unusual if more than 10 of them have hypertension?