Answer
(a) $2298$
(b) $18384$
(c) See graph below.
Work Step by Step
(a) Model the population with an exponential function of base $2$ as $P(t)=P_02^{kt}$
where $P_0$ is the initial population and $k$ is a constant.
Since $P(10)=2P_0$, we have $2^{10k}=2$ and get $k=\frac{1}{10}$
At $t=25$, we have $P(25)=P_02^{25/10}=13000$ which gives $P_0=2298$
(b) At $t=5+25=30$, we have $P(30)=2298\times2^{30/10}=18384$
(c) The bird population function can be graphed as shown in the figure.