In general, what kind of people earn the most money? people with skills that are in high demand and high in supply people with skills that are in high demand but low in supply people with skills that are in low demand and low in supply people with skills that are in low demand but high in supply

This actually depends in some instances. I know this may be crazy to say at first but I studied Economics, Business and Public Policy at UNI and this was probably one of my favourite lectures because the professor kicked a hole in the wall. Back to the answer. Generally speaking people with High Demand skills and low supply earn the most money however in many instances these skills they possess could be done by many other people however the course of actions to get the job and is major role bumps up the income. For example: A ceo's position can be filled by many people in a multinational company. However as a result of the shear work load and the time spent moving your way up the ranks to get this promotion you expect a high pay, I would too. Another example: In my country Australia the minimum wage is $14 ($9 US) therefore some jobs (like servers) can make more money even though these jobs are oversupplied as they receive both tips and a high wage (compared to overseas)

Alloy of metals is the answer