cache.txt

 apt-cache policy apache2
apache2:
  Installed: 2.4.16-4+deb.sury.org~trusty+3
  Candidate: 2.4.16-4+deb.sury.org~trusty+3
  Version table:
 *** 2.4.16-4+deb.sury.org~trusty+3 0
        500 http://ppa.launchpad.net/ondrej/apache2/ubuntu/ trusty/main amd64 Packages
        100 /var/lib/dpkg/status
     2.4.7-1ubuntu4.5 0
        500 http://us-east-1.ec2.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu/ trusty-security/main amd64 Packages
     2.4.7-1ubuntu4 0
        500 http://us-east-1.ec2.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages

install.txt

sudo apt-get install apache2-mpm-prefork 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 apache2-mpm-prefork : Depends: apache2 (= 2.4.7-1ubuntu4.5) but 2.4.16-4+deb.sury.org~trusty+3 is to be installed
E: Unable to correct problems, you have held broken packages.

prefork.txt

sudo a2enmod mpm_prefork 
Considering conflict mpm_event for mpm_prefork:
ERROR: Module mpm_event is enabled - cannot proceed due to conflicts. It needs to be disabled first!
Considering conflict mpm_worker for mpm_prefork: