In a particular retail clothing store, approximately 20% of potential customers who walk into the store make a purchase. In a random sample of 25 customers that walked into the store,

a. what is the probability that exactly 11 of the customers make purchases?

Round to 3 significant digits.

b. what is the probability that at least 2 of the customers make purchases?

Round to 3 significant digits.

c. how many of the customers are expected to make purchases?

Round to 3 significant digits.

d. what is the standard deviation of the number of customers who make purchases?

Round to 3 significant digits.