Answer:
The appropriate probability model for X is a Binomial distribution,
X
Bin (<em>n</em> = 5, <em>p</em> = 1/33).
Step-by-step explanation:
The random variable <em>X</em> can be defined as the number of American births resulting in a defect.
The proportion of American births that result in a birth defect is approximately <em>p</em> = 1/33.
A random sample of <em>n</em> = 5 American births are selected.
It is assumed that the births are independent, i.e. a birth can be defective or not is independent of the other births.
In this experiment the success is defined as a defective birth.
The random variable <em>X</em> satisfies all criteria of a Binomial distribution.
The criteria are:
- Number of observations is constant
- Independent trials
- Each trial has only two outcomes: Success and Failure
- Same probability of success for each trial
Thus, the appropriate probability model for X is a Binomial distribution, Bin (<em>n</em> = 5, <em>p</em> = 1/33).
Answer:

Step-by-step explanation:
![S= \frac{n}{2 [2a + (n - 1)d]}](https://tex.z-dn.net/?f=S%3D%20%5Cfrac%7Bn%7D%7B2%20%5B2a%20%2B%20%28n%20-%201%29d%5D%7D)
Simplifying the fraction by multiplying d into the (n-1) term,
![s=\frac{n}{2 [2a + (n - 1)d] } = \frac{n}{2[2a + dn - d] }](https://tex.z-dn.net/?f=s%3D%5Cfrac%7Bn%7D%7B2%20%5B2a%20%2B%20%28n%20-%201%29d%5D%20%7D%20%3D%20%5Cfrac%7Bn%7D%7B2%5B2a%20%2B%20dn%20-%20d%5D%20%7D)
Simplifying the fraction by multiplying 2 throughout,

Multiply
on both sides

Cancel the
on the right hand side

Multiply s to the terms,

Move
to the right hand side by subtracting
on both sides

On the right hand side of the equation, take out 

Divide Left hand side by
,

They would cost the same amount by day 2. day 1 for car a is $45.50. day 1 for car b is $40. day 2 for car a is $60. day 2 for car b is also $60.