What is the marginal revenue from producing the fourth unit?

Refer to the figure above. What is the equilibrium quantity after the demand curve shifts to D2?

A) 20 units B) 30 units C) 35 units D) 50 units

Which of the following statements is true?

A. Current account balance = -(capital account balance). B. A country's balance on current account equals its balance on capital account. C. If the market for a nation's currency is in equilibrium, a capital account surplus necessarily means a current account surplus. D. Capital accounts and current accounts balances are determined by governments.