Answer:
Change in US external wealth between periods T and T +1 in dollars = -$100
Step-by-step explanation:
Since nothing else changes, this implies that the exchange rate per yen is $0.01 in periods T and T +1. Therefore, we have:
Value shares of Sonic in period T in dollar = Number of shares of Sonic bought in period T * Price per share of Sonic in Yen in period T * Exchange rate per yen in periods T = 100 * 700 * $0.01 = $700
Value shares of Sonic in period T+1 in dollar = Number of shares of Sonic in period T+1 * Price per share of Sonic in Yen in period T+1 * Exchange rate per yen in period T+1 = 100 * 600 * $0.01 = $600
Change in US external wealth between periods T and T +1 in dollars = Value shares of Sonic in period T+1 in dollar - Value shares of Sonic in period T in dollar = $600 - $700 = -$100