Answer:
Balance after 30 years = $151,018.50
Explanation:
In order to calculate this, we will calculate the future value on an amount invested, gaining interest over the years of investment, and this is given by:

where:
FV = future value
PV = present value
r = interest rate
t = time in years.
Hence the future value is calculated as follows:
1. For the first 10 years at 7% interest:
7% interest = 7/100 = 0.07


2. For the last 20 years at 9.5%(0.095) interest:
Note that for the remaining 20 years, the present value (PV) used = 24,589.392, as ending balance after the first 10 years


Total Future value earned = $151,018.50