Need help solving this math question?

Hey..so I can't remember ANYTHING from data management, and a friend of mine needed help solving this question:





1.Credit card companies are increasing their revenues by raising the late fee charges to their customers. In a recent year, 15% of all credit card customers had to pay a late fee. A random sample of 20 credit card holders is selected,





a)What is the expected number of customers who had to pay a late fee?





b)What is the probability that 0 customers had to pay a late fee?





c)What is the probability that no more than 3 customers had to pay a late fee?





d)What is the probability that no more than 10 customers had to pay a late fee?





Thanks in advance for any help

Need help solving this math question?
1.a) .15 x 20 = ANSWER


b) 1 - .15 = .85 x 20 = ANSWER


c) 1/20 X .15 + 2/20 X .15 + 3/20 X .15 = ANSWER


d) 1/20 X .15 + 2/20 X .15 + 3/20 X .15 + .... + 9/20 X .15 + 10/20 X .15 = ANSWER





... = in between.
Reply:Probability of paying late fee =0.15





a20 x 0.15= 3


b 1 - 0.15=0.85


c From a 0.15


d 3x0.15=0.45