Answer:
$900
Explanation:
The formula for simple interest is I = PRT where I is the interest earned, P is the principal/amount deposited or borrowed, R = rate as a decimal, and T = time in years
I = PRT
I = (500)(0.04)(20)
I = 400
Add the interest to the principal, and she will have $900 in 20 years.
Please let me know if you have questions about this.