Answer
(a). $h=0.7565$
(b). $n(3)=156233.42$
Work Step by Step
The formula for exponential population growth is, $n(t)=n_0e^{rt}$. Whereas, $n_0$ is the Initial population, $r$ is the growth rate, and $n(t)$ is the population at time $t$.
$n_0=10000$, $t=1, n(1)=25000$,
(a). $n(t)=n_02^{t/h}$, Whereas $h$ is the doubling time.
Therefore, $n(1)=10000\times2^{1/h}=25000$,
$2^{1/h}=2.5$,
$\frac{1}{h}\log 2=\log2.5$,
$h=0.7565$
(b). $n(3)=10000\times2^{3/0.7565}=156233.42$
