Option 1 -> Brokerage is payment for a current service provided, so it is included in national income.
Option 2 -> Interest paid by production units is a factor payment for capital, included in national income.
Option 3 -> GST is an indirect tax, which is a transfer payment to government, not included in national income.
Option 4 -> Interest paid by banks is a factor income for capital provided by depositors, included in national income.
Hence, Payment of GST by firms to the government -> National income is calculated at factor cost, which includes only payments made to factors of production (land, labor, capital, and entrepreneurship). GST and other indirect taxes are transfer payments that do not represent any productive service or factor income. They are simply transfers from firms to the government and are excluded when calculating national income at factor cost. To convert national income at market prices to factor cost, we subtract indirect taxes and add subsidies. -> correct