Answer:
$132.93
Explanation:
We will use annuity formula, which is:
![P=C[(1-(1+r)^(-n))/(r)]](https://img.qammunity.org/2020/formulas/mathematics/middle-school/pt82b697ydpsift2yklpg64ix15hhch4tg.png)
Where P is the loan amount
C is the monthly payment
r is the rate of interest [monthly]
n is the time period [in months]
Firstly, let's calculate her normal monthly payment (without purchasing points):
P is 105,000
C is what we need to find
r is the 0.045/12 = 0.00375
n is 12*30 = 360
Now, we have:
![P=C[(1-(1+r)^(-n))/(r)]\\105,000=C[(1-(1+0.00375)^(-360))/(0.00375)]\\105,000=C[197.3612]\\C=532.02](https://img.qammunity.org/2020/formulas/mathematics/middle-school/3pxjm419jap7qbf9ors3fzhzlivd5zbich.png)
So monthly payment would be around $532.02
Now,
With each point purchase, the interest rate goes down by 0.25%, so for 2 points it will be 4.5% - 2(0.25) = 4%
Also, since 20% downpayment, the loan amount would be (0.8)(105,000) = 84,000.
Now, putting these values into the annuity formula we have:
![84,000=C[(1-(1+0.0033)^(-360))/(0.0033)]\\84,000=C(210.4766)\\C=399.09](https://img.qammunity.org/2020/formulas/mathematics/middle-school/soygqru9knhts8y4qohrpupzn7xwijb5wv.png)
The monthly payment would be around $399.09
The amount that is lower is 532.02 - 399.09 = $132.93