MATH
posted by Paul .
From experience, the manager of Kramer's Book Mart knows that 40% of the people who are browsing in the store will make a purchase. What is the probability that among ten people who are browsing in the store, at least four will make a purchase? (Round your answer to four decimal places.)

at least four make a purchase?
pr(at least four)=Pr(4)+pr(5)+...
= p^4q^6+P^5q^5+p^6q^4+p^7q^3+...p^10q^0
where p=.4, q=.6