1. Why is it important to understand the mental process behind people's decision making?

2. Why are short-run total costs partly fixed and partly variable costs, and why are long-run costs entirely variable?

3. Why is price equal to marginal revenue and also equal to average revenue for the purely competitive firm?

4. In what way does an "invisible hand" work to ensure an efficient allocation of society's scarce resources?

Please provide any references I can look for an example or more in depth information.