Binary router/switch question

in CCNA & CCENT
If we assign the IP address 00001010.11111110.00000001.00001001 and the subnet mask 11111111.11111111.11111111.11111000 to a switch, what is the default IP address of the router?
Answer: 00001010.11111110.00000001.00001110
How to calculate this? It's not a logic operation, not AND, not OR, not XOR.
Comments
10.254.1.9/29 (255.255.255.248) is part of the 10.254.1.8/29 subnet, meaning the usable host range is: 10.254.1.9 - 10.254.1.14.
Their answer is 10.254.1.14, but you could assign any unused IP address in that range to a router.
I guess convention can be to set the last usable host as the gateway (like most home routers being something similar to 192.168.1.254 by default), but I just don't like this question at all. There is no hard and fast correct answer to this, unless I'm missing something. Correct me if I'm mistaken.
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Ah, right. That makes sense. No problem!
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