Answer:
You will need to contribute $2,856.55 at the beginning of each period to reach the future value of $23,000.00.
Explanation:
Future value of investment = $23,000
Number of period = 7 years
Interest rate = 3.5% compounded annually
Using an online finance calculator:
FV (Future Value)	$23,000.01
PV (Present Value)	$18,077.80
N (Number of Periods)	7.000
I/Y (Interest Rate)	3.500%
PMT (Periodic Payment)	$2,856.55
Starting Investment	$0.00
Total Principal	$19,995.82
Total Interest	$3,004.19