A chemical discharge from the factories along the Pearl River causes a total damage worth of $50 million in 25 years. The Chinese government decides to demand that damage cost this year (2015) from the International sports garment companies through a tax policy. However, Environmental Ministry uses a discount factor of 1 and comes up with a Net Present Value while the Commerce Ministry uses a 10% discount rate and comes up with another Net Present Value of the damage cost.

a) Calculate both the NPVs and explain which discount rate offers a more sustainable option in this case.

b) Name two types of discount rate schedule. For US environmental projects EPA uses which kind of discount rate schedule?

This is the whole given question