$4.$ A mining company is considering a new project. Because the mine has received a permit, the project would be legal but it would cause significant harm to a nearby river. The firm could spend an additional $$10$ million at Year $0$ to mitigate the environmental problem, but it would not be required to do so$.$ Developing the mine $($without mitigation$)$ would require an initial outlay of $$60$ million, and the expected cash inflows would be $$20$ million per year for $5$ years. If the firm does invest in the mitigation, the annual inflows would be $$21$ million per year for $5$ years. The risk$-$adjusted WACC is $12\%.$

a$.$ Calculate the NPV and IRR with mitigation and without mitigation.

b$.$ How should the environmental effects be dealt with when this project is evaluated?

c$.$ Should this project be undertaken? If so$,$ should the firm do the mitigation?