A. nothing because you found the money.
B. Rs20 (because you found the money Rs 20 to buy other things) plus the value of your time spent at the game.
C. Rs 20 (because you could have used the Rs 20 to buy other things) plus the value of your time spent at the game plus the cost of the dinner you purchased at the game.
D. Rs20 (because you could have used the Rs20 to buy other things)