How does this work ?

Q. the DMZ inerface has a higher security level then the partnernet interface. Given the configuration that follows, which address will server
172.16.0.55 appear as when communicating with hosts on the partnernet network?

static (DMZ,partnernet) 172.18.10.64 172.16.0.32 netmask 255.255.255.224

A. 172.18.10.55
B. 172.16.0.55
C. 172.18.10.87
D. 172.18.0.87
E. none of these answers are correct

I thought E. quizzer says C is correct, I can't see how they got this answer.

_________________
"If you're good at anticipating the human mind. It leaves nothing to chance."
-Jigsaw

Well I'm not sure if this is how it actually works, but 172.16.0.55 is the 23rd ip in its subnet and so is 172.18.10.87.
So it would imply that the device keeps track of this when doing the translation.