the value of the certificate was 1967.68 when you were 9 years old and 4839.72 when you were 18. how did your parents out into the certificate at your birth?

Question

it has a locked in interest rate 

Answer 1

They put in $800 at 10.5171 % interest.

10.5171  $800
1     884.1368
2     977.1223514
3   1079.887286
4   1193.460112
5   1318.977505
6   1457.695689
7   1611.003002
8   1780.433799
9   1967.683802
10  2174.622873
11 2403.330135
12 2656.090769
13 2935.434491
14 3244.157072
15 3585.348316
16 3962.422984
17 4379.154971
18 4839.715079