Okay, so I'm stuck on this question:

You decide to play a game. The rules for the game is that there are 8 question that you need to answer. For each question, you are given 4 different options for answer.

Before you start a game, you have to place a starting bid. When all 8 questions have been answered, the following prizes are given:

If all 8 questions have been answered correctly, you get 1000 times your starting bid back.

If 7 questions have been answered correctly, you get 100 times your starting bid back.

If 6 questions have been answered correctly, you get 10 times your starting bid back.

5 correct answers and below, does not get you any prizes.

You use a starting bid of $100.

How many questions would you have to know the answer to, before you in average get a profit from this game?
So basically, I believe that you need to consider the fact that it's a conditional probability, since the chance of getting a prize goes up for every question that you know the answer to. But I just can't figure this out.