Ce sont des maths en anglais

Mail-order marketing
companies have a response rate of 15% to their advertising flyers.

a) Compute the probability that exactly 3 people out of a sample of 20 respond to the flyers they receive.

b) Find the expected number of people in a sample of 20 who will respond to the flyers.

c) Compute the probability that at least 3 people out of a sample of 20 respond to the flyers they receive.

Merci