how to sovle

Going skiing will cost Adam $80 a day. He also loses $40 per day in wages because he has to take time off from work. Adam still decides to go skiing. () His decision is rational if Adam's marginal benefit of spending a day skiing is greater than his marginal cost. () The $80 price of skiing is not an opportunity cost and so did not affect Adam's decision. () He loses a total of $120 per day, so his decision is irrational. ) Adam's lost $40 per day in wages is not an opportunity cost and so did not affect his decision. ( Adam is definitely making a decision that is in the social interest