/usr/lib/mono/4.5/mod-mono-server4.exe is in mono-apache-server4 3.8-2.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/mono/4.5/../gac/mod-mono-server4/3.8.0.0__0738eb9f132ed756/mod-mono-server4.exe