Scarcity — the permanent human condition: wants are unlimited and renewable; resources (land, labour, capital, time) are limited. Note: scarcity is relative (resources vs wants), not absolute (a poor family's rice shortage and a billionaire's shortage of hours are both scarcity).
Choice — scarcity forces choice; and every choice has an opportunity cost: the value of the next-best alternative forgone. (Legal illustration: a government's budget allocated to airports cannot build provincial courts; an hour in litigation is an hour not billed elsewhere — opportunity cost is why "time is money" in court reform debates.)
The economic problems (every society, every ism, must answer):
1. What to produce — and in what quantities (rice or hydropower; guns or schools)?
2. How to produce — which technique (labour-intensive or capital-intensive; organic or chemical)?
3. For whom to produce — how is output distributed (the equity question)?
4. How to grow — how much to consume now vs invest for tomorrow?
5. Full employment and stability — are resources used, and are prices stable?
The mechanisms: tradition (the village economy), the market (prices answer the questions — capitalism), the command state (planning answers them), and every real economy — Nepal's included — is a mixed economy: market answer for most goods, state answer for courts, defence, roads, monetary policy. For a law student: each mechanism has a legal constitution — contract and property law for the market; administrative and planning law for the state.