According to economists, which of the following is a good predictor of human behavior in most situations?

"Lady Gaga concert sells out. 60,000 tickets sold." What can an economist conclude from the above headline?

A) There is a surplus of tickets. B) The market clears. C) The quantity supplied is 60,000. D) The quantity demanded is at least 60,000. E) Both C and D above.

Refer to the above figures. If a positive externality that existed becomes corrected, price and quantity will become

A) P1 and Q1. B) P2 and Q2. C) P3 and Q3. D) P4 and Q4.