To calculate the contestant's balance of prize money, we need to find out how much he lost from answering 6 questions wrong.
The contestant loses $12.50 for each wrong answer. Therefore, for 6 wrong answers, the total loss can be calculated as follows:
\[ \text{Total Loss} = \text{Number of Wrong Answers} \times \text{Loss per Wrong Answer} \] \[ \text{Total Loss} = 6 \times 12.50 = 75.00 \]
Since he has not answered any questions correctly, his overall balance of prize money would be:
\[ \text{Balance} = -\text{Total Loss} = -75.00 \]
So the contestant's balance of prize money is:
\[ \boxed{-75.00} \]
The correct response is −$75.00.