Food Shelters $\quad$ (Refer to Example $10 .$ ) For three food shelters, monthly food costs $F$ in dollars, number of people served per month $N$, and monthly charitable receipts $R$ in dollars are as shown in the table.
$$
\begin{array}{ccc}
\begin{array}{c}
\text { Food } \\
\text { Costs }(F)
\end{array} & \begin{array}{c}
\text { Number } \\
\text { Served }(N)
\end{array} & \begin{array}{c}
\text { Charitable } \\
\text { Receipts }(R)
\end{array} \\
\hline 1300 & 1800 & 5000 \\
5300 & 3200 & 12,000 \\
6500 & 4500 & 13,000
\end{array}
$$
(a) Model these data using $F=a N+b R+c,$ where $a, b,$ and $c$ are constants.
(b) Predict the food costs for a shelter that serves 3500 people and receives charitable receipts of $\$ 12,500$. Round your answer to the nearest hundred dollars.