Q4. Assuming an economy with no government and no foreign trade, calculate the GDP for the following scenario. There are three firms, firm A is a mining company, firm B is a steel producer and firm C is an automobile manufacturer. In a specific year, firm A sells $100 million worth of iron to firm B, firm B sells $200 million worth of steel to firm C and firm C sells $500 million automobiles to general public. If there are no changes in inventory, no taxes and no other producers in the economy, what is GDP?