Answer: c. $15 million
Step-by-step explanation:
If you get your casino building first, your competitor will have to get the Hotel so as to make $5 million which is more than the $3 million if they were to choose a casino as well.
The Payoff for you would therefore be $20 million and for them $5 million.
The Net Payoff over your competitor would be = 20 - 5
= $15 million