can somone explain to me these questions? thank you!

1) What do we mean by opportunity cost? Give a real example where you experienced and practice opportunity cost. 2) Briefly explain the mechanics of circular flow? what do you mean by invisible hand"? 3) What is the difference between Quantity demanded and Demand? Quantity supplied and supply? what causes Demand and supply to shift? what will happen to equilibrium price and quantity if both supply and Demand increases( both shifts right) 4) What is Government role and where is its failure? Please be be very brief 5) Name three major issues that economists are interested for any economy ? Why shocks and sticky price are responsible for short run economic fluctuation