Preserving or mining a canyon

Suppose you are asked to decide on the appropriate use of a scenic canyon. At the moment, the canyon is used as a park but a mining company has proposed converting it into a coal mine. You are given the following information:

• There are 10,000 people who visit the park each year and their use is nonrival.
• Each visitor’s marginal benefits from Qi visits are given by MBi= A – B*Qi
• The park is free and there are 30,000 visits each year
• As an experiment, a few years ago visitors were charged $2 for each visit. The total number of visits dropped to 25,000.
• The mining company would be willing to pay $1 million for the land.
• The interest rate is 10%.

Calculate the total social benefits that visitors receive from the park each year when no entry fee is charged. Be sure to show your work and make your reasoning clear. Using this information, determine what should be done with the land and then explain your result in words.