93. How many five-digit numbers are there in which no two digits of the same parity stand next to each other?
93. The first digit can be chosen in nine ways. The second digit must have a parity different from that of the first digit. In any case, the second digit can be chosen in five ways. The third, fourth, and fifth digits can also be chosen in the same number of ways. Therefore, the number of required five-digit numbers will be $9 \cdot 5 \cdot 5 \cdot 5 \cdot 5=5625$.