The Trade- Weighted Index (TWI) of the Exchange Rate

The trade- weighted index (TWI) of the exchange rate:

A) is less relevant than bilateral rates when looking at the impact of the exchange rate on the economy.
B) is set by the RBA and remains fixed until the government alters exchange rate policy.
C) is composed of weights based on econometric estimates of exchange rate elasticities with the A$.
D) measures the average value of the A$ against all overseas currencies.