I'm not sure of this question. Thanks for the help!

Eloise pays $40 for a daily pass to the ice skating centre. When inside the centre, Eloise considers how many hours of training she should complete. She expects to gain an incremental benefit of $60 from the first hour, then gain subsequent incremental benefits of $50 from the second, $30 from the third, $20 from the fourth and $5 from the fifth The cost of each hour of training is $20. In determining how many hours to train for, the daily pass is a/an cost. Using marginal analysis, Eloise should train for many hours? Type A for Average cost, M for Marginal cost, S for Sunk cost or O for Opportunity maximum surplus for Eloise, from training the number of hours you found in part b, is S Answer to the nearest whole number (with no decimal places)