Answer:
The monthly payment is $316.54.
Step-by-step explanation:
It is given that Charlotte purchased a pool for $7680. The rate of interest is 20.45%.
She use a six-month deferred payment plan with an interest rate of 20.45%.

The principle amount after six-month deferred payment is

![PV=C\times [\frac{1-(1+r)^{-n}}{r}]](https://tex.z-dn.net/?f=PV%3DC%5Ctimes%20%5B%5Cfrac%7B1-%281%2Br%29%5E%7B-n%7D%7D%7Br%7D%5D)
Where, PV is present value, C is monthly payment, r is rate of interest and n is number of years.
![8465.28=C\times [\frac{1-(1+(\frac{0.2045}{12})^{-36}}{\frac{0.2045}{12}}]](https://tex.z-dn.net/?f=8465.28%3DC%5Ctimes%20%5B%5Cfrac%7B1-%281%2B%28%5Cfrac%7B0.2045%7D%7B12%7D%29%5E%7B-36%7D%7D%7B%5Cfrac%7B0.2045%7D%7B12%7D%7D%5D)

Therefore the monthly payment is $316.54.