I think the answer would be purpose. I'm not sure though.
The interview is like an informal and formal one. A lot is expected to an interview. It doesn't really have to be formal or not because everything is subjective. It is informal compared to an essay. It is formal compared to a speech.
Answer: the formation of a mental image of something.
Explanation: basically you have the mental image in your head of what is being described to you.
The punctuation is correct if that is how how the statement started and ended.