The way the game works is you are given three dice - one six-sided die, one ten-sided die and one twenty-sided die. It costs $1 to play the game and if you roll the three dice and get a total of exactly 21 you win $21 (which includes the dollar you wagered). If you do not get 21 exactly then you lose the $1 you wagered.
1. What is the probability of getting 21 when rolling the three dice?
2. What is the expected value of the winnings for a person playing this game once?
3. What other totals of the three dice would have the same expected value as rolling 21? Explain your answer.