What file should you look at first when installing tower?

What keyword sets a change condition for a given task?

Create a playbook /home/bob/ansible/timesync.yml that runs on hosts in the webservers host group and does the following:
* Uses the timesync RHEL system role.
* Sets the ntp server to 0.uk.pool.ntp.org
* Sets the timezone to UTC

Install and configure ansible
User bob has been created on your control node. Give him the appropriate permissions on the control node.
Install the necessary packages to run ansible on the control node.
Create a configuration file /home/bob/ansible/ansible.cfg to meet the following requirements:
* The roles path should include /home/bob/ansible/roles, as well as any other path that may be required for the course of the sample exam.
* The inventory file path is /home/bob/ansible/inventory.
* Ansible should be able to manage 10 hosts at a single time.
* Ansible should connect to all managed nodes using the bob user.
Create an inventory file for the following five nodes:
nodel.example.com
node2.example.com
node3.example.com
node4.example.com
node5.example.com
Configure these nodes to be in an inventory file where node1 is a member of group dev. nodc2 is a member of group test, nodc3 is a member of group proxy, nodc4 and node 5 are members of group prod. Also, prod is a member of group webservers.

Which variable name is invalid?