The contraction of money supply in the economy can be influenced by the central bank's actions in the following ways: 1. **Purchase of Treasury Bills by the central bank from the public**: This action increases the money supply. When the central bank purchases Treasury bills, it injects money into the economy, thereby increasing the money supply. 2. **Sale of Treasury Bills by the central bank to the public**: This action decreases the money supply. When the central bank sells Treasury bills, it takes money out of circulation, thereby reducing the money supply. 3. **Sale of foreign exchange by the central bank**: This action can also lead to a contraction of the money supply. When the central bank sells foreign exchange, it absorbs domestic currency from the market, reducing the money supply. 4. **Purchase of foreign exchange by the central bank**: This action increases the money supply. When the central bank purchases foreign exchange, it releases domestic currency into the market, increasing the money supply. Therefore, the actions that lead to a contraction of money supply are the sale of Treasury Bills by the central bank to the public and the sale of foreign exchange by the central bank. Hence, the correct option is 3: 2 and 3 only.