How to transform this word problem into a binomial distribution equation

[6021023]

Homework Statement

Because not all airline passengers show up for their reserved seat, an airline sells 125 tickets for a flight that holds only 120 passengers. The probability that a passenger does not show up is 0.10, and the passengers behave independently

a) What is the probability that every passenger who shows up can take the flight?
b) What is the probability that the flight departs with empty seats?

Homework Equations

f(x) = n nCr x p^x(1 - p)^n-x

The Attempt at a Solution

a) 125 nCr 120 (0.9)^120*(0.1)^5

b) 125 nCr 0 (0.9)^0 * (0.1)^125

 

[rosh300]

let n be the number of passengers and p be the probability they won't turn up.
(a)find prob less than or equal to 5 don't turn up
(b)similar thing as (a)