A chess king is said to attack all the squares one step away from it, horizontally, vertically, or diagonally. For instance, a king on the center square of a 3 \times 3 grid attacks all 8 other squares, as shown below. Suppose a white king and a black king are placed on different squares of a 3 \times 3 grid so that they do not attack each other. In how many ways can this be done?
Answer Choices
A. 20
B. 24
C. 27
D. 28
E. 32