Given data:
The given principal is P=$20,000.
The given rate of interest is r=6%.
The given time is t=20 years.
The expression for the interest is,
![I=P(1+(r)/(100))^t-P](https://img.qammunity.org/2023/formulas/mathematics/high-school/cycfdoalkb0yu4d7nkpbo2g6578r7dc2th.png)
Substitute the given values in the above expression.
![\begin{gathered} I=20,000(1+(6)/(100))^(20)-20,000 \\ =20,000(1.06)^(20)-20,000 \\ =44,142.71 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/rbdygc1lcylgnj1kh6ekt7qbi8k3e9x2nr.png)
Thus, the interest earned after 20 years is $44,142.71, so (C) option is correct.