11. After the pastry chef finishes baking a large rectangular cake, he plans to cut it into identically sized rectangular pieces along directions parallel to the edges of the pan, without ever cutting all the way through. The pastry chef also intends to make the edges of the pan into the same number of crispy edges, which will be mixed with the rectangular pieces to form brownies. How many brownies can the pastry chef make at most?
(A) 24
(B) 30
(C) 48
(D) 60
(E) 64
11. D.

As shown in Figure 10, let the length of the rectangular pan be $m$ and the width be $n$.
$$
\begin{array}{l}
\text { Then }(m-2)(n-2)=\frac{1}{2} m n \\
\Rightarrow m n-4 m-4 n+8=0 \\
\Rightarrow(m-4)(n-4)=8 \\
\Rightarrow(m-4, n-4)=(8,1) \text { or }(4,2) \\
\Rightarrow(m, n)=(12,5) \text { or }(8,6) .
\end{array}
$$

Since $12 \times 5=60>8 \times 6=48$, the baker can make a maximum of 60 brownies.