Remember that
The compound interest formula is equal to
where
A is the Final Investment Value
P is the Principal amount of money to be invested
r is the rate of interest in decimal
t is the number of Time Periods
n is the number of times interest is compounded per year
in this problem we have
r=1.21%=0.0121
P=$4,300
t=2 years
n=1
substitute in the formula above