Answer:
The probability is 
Step-by-step explanation:
From the question we are told that
The capacity of an Airliner is k = 300 passengers
The sample size n = 320 passengers
The probability the a randomly selected passenger shows up on to the airport

Generally the mean is mathematically represented as
=>
=>
Generally the standard deviation is

=> 
=> 
Applying Normal approximation of binomial distribution
Generally the probability that there will not be enough seats to accommodate all passengers is mathematically represented as

Here 
=>
Now applying continuity correction we have
=> ![P(X >300 ) = P(Z > \frac{[300.5] - 307.2}{3.50} )](https://tex.z-dn.net/?f=P%28X%20%20%3E300%20%29%20%3D%20%20P%28Z%20%3E%20%20%5Cfrac%7B%5B300.5%5D%20-%20307.2%7D%7B3.50%7D%20%29)
=> 
From the z-table

So

Answer:
0.5981 = 59.81% probability that three or less of the selected adults have saved nothing for retirement
Step-by-step explanation:
For each adult, there are only two possible outcomes. Either they save nothing for retirement, or they save something. The probability of an adult saving nothing for retirement is independent of any other adult. This means that the binomial probability distribution is used to solve this question.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.

In which
is the number of different combinations of x objects from a set of n elements, given by the following formula.

And p is the probability of X happening.
20% of adults in the United States save nothing for retirement (CNBC website).
This means that 
Suppose that sixteen adults in the United States are selected randomly.
This means that 
What is the probability that three or less of the selected adults have saved nothing for retirement?
This is:

In which






0.5981 = 59.81% probability that three or less of the selected adults have saved nothing for retirement
The tax is $2.80 but the total is $42.80