any one should help me please
About 55% of emergency room visits are unnecessary. Assuming each emergency room visit is independent. (Hints: first define the random variable X. Then write the objective of each question in terms of X.)
a) If you randomly select 15 patients from those visiting the emergency department, what is the chance that all of them need to be in the emergency room?
b) What is the expected number from the 15 randomly selected patients, who don’t need to be in the emergency room and what is the standard deviation of that number?

Question

any one should help me please
About 55% of emergency room visits are unnecessary. Assuming each emergency room visit is independent. (Hints: first define the random variable X. Then write the objective of each question in terms of X.)
a)	If you randomly select 15 patients from those visiting the emergency department, what is the chance that all of them need to be in the emergency room? 
b)	What is the expected number from the 15 randomly selected patients, who don’t need to be in the emergency room and what is the standard deviation of that number?