we knows total amount owed (A) = P $(1 + \frac{r}{100}) ^{n}$
and it's given that industrial power is doubled from 2000-2001 to 2010-2011.
So, here n=10 and A = 2P
$2P=P(1 + \frac{r}{100}) ^{10}$
$2=(1 + \frac{r}{100}) ^{10}$
$2^{\frac{1}{10}}=(1 + \frac{r}{100})$
$1.07177=(1 + \frac{r}{100})$
$.07177=( \frac{r}{100})$
r=7.17≃7.2
Hence,Option (B)7.2 is the correct choice.