It is a hot day at the beach. Ice water costs $1 per bottle and this is your only option. Your marginal benefit for water follows the equation MB = $10 – $x.

x is represents the number of bottles of ice water you have had. So, for example, the marginal benefit of the first bottle is $10 – $1 = $9. The MB of the 2nd bottle is $8 .. and so on.

Assuming you are an economically rational consumer how much consumer surplus will you achieve when you are done for the day?