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

In a random sample of 20 customers that walked into the store,

a.what is the probability that exactly 10 of the customers make purchases? Round to 4 significant digits.

b.what is the probability that at least 2 of the customers make purchases? Round to 4 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 4 significant digits.