For the 1st question on mining.
I put for the 25 marker negative externalities. I drew a negative externalities of production diagram with MPC greater than MSC. Mining is a negative externality. I then defined negative externalities etc.
I then talked about what would happen if the government didn't intervene, i.e. environment will become perhaps so bad that it could not be cleaned up! Firms will be doing whatever they wish, i.e. polluting lakes.
I then went on to say what government intervention could happen i.e. maximum pricing, reducing the incentive to mine for rare-earth metals as China can not price the metals at whatever it wants, this decreases its profits. Regulations, i.e. banning pollution in rivers and a certain amount of pollution can be released. Pollution permits could be used to benefit firms who do not pollute as they can sell pollution permits who need it. However, there will be an incentive for firms to decrease pollution as their costs will decrease.
Throughout it all I evaluated and concluded at the end.