B. Abigail used less than Carly and the total was 109.
Answer:
The equation can be used to determine the amount of money S(t) that her savings account has after t years is 
Step-by-step explanation:
A student invests $500 in a savings account
Principal = $500
Rate of interest = 4% = 0.04
We are supposed to find equation can be used to determine the amount of money S(t) that her savings account has after t years
Formula : 
Where A is the amount after t years =S(t)
t = time
r = rate of interest in decimals =0.04
P = Principal=500
Substitute the value in the formula :
So, 

Hence The equation can be used to determine the amount of money S(t) that her savings account has after t years is 
$12.89 should be the answer bc 4.5+2.25=6.75 and 87 divided by 6.75 is 12.888888 so i would either round up or down