To find how much interest is earned after 6 years, we apply the following formula:

where:
- P = amount initially invested = $20,000
- r = percentage rate at which the amount was invested = 4.5
- t = the duration for which the investment was made = 6 years
- n = the frequency at which the interest is compounded = quarterly = 4
Now, we simply substitute the values into the formula to obtain the Interest, as follows:



Therefore, the interest earned after 6 years is: $6,160