In order to solve this, we have to use the compound interest formula given by the following expression:
![A=P(1+(r)/(n))^(nt)](https://img.qammunity.org/2023/formulas/mathematics/high-school/39foo2gerf9tf1ffk32zwshrn339mz02kv.png)
Where r is the interest rate, P is the initial amount deposited, n the number of times the period is compounded a year, t the year, and A the final amount.
By replacing 0.0645 (6.45%) for r, 4 for n, 3 for t and 5500 for P into the above equation, we get:
![A=5500(1+(0.0645)/(4))^(4*3)=6663.8978](https://img.qammunity.org/2023/formulas/mathematics/college/nsb0yojnnwo6zvtxsb5bphbhwf8xn7kan1.png)
Then, after 3 years you will have $6663.9.
In order to determine the APY, we can use the following formula:
![APY=100*((1+r/n)^n-1)](https://img.qammunity.org/2023/formulas/mathematics/college/scx6g3qn7aker0min66yua39lngne4rjgw.png)
Where n is the number of times the interest is compounded a year (4) and r is the rate of interest (0.0645), then we get:
![APY=100*((1+0.0645\/4)^4-1)=6.61](https://img.qammunity.org/2023/formulas/mathematics/college/72746krkntte67cnpdv01vfchtlxbuw8j6.png)
Then, the APY equals 6.61%