kompound interest
tu dubel yer munee in 17 yeers
assume kompount per yeer
(1+r)^17=2
log[(1+r)^17] = log(2)
17*[log(1+r)] =log(2)
log(1+r) =log(2)/17
for base=10, log(2)=0.301029995
divide bi 17...0.017707646
10^0.017707646=1.041616
so r=0.041616...4.1616%