compundinterest
F=P(1+(r/n))^(nt)
F=future value
P=present value
r=rate in decimal form
n=number of times per yera it is compunded
t=time in years
P=20000
r=0.03
12 months per year so n=12
t=15
F=20000(1+(0.03/12)^(12*15)
F=20000(1.0025)^(180)
F=20000(1.56743)
F=31348.634
round
$31348.63
B is answer