3. (1) A customs duty at the rate of one per cent ad valorem shall be levied on all articles included in the Schedule which are exported from Bangladesh: Provided that the said duty shall not be levied on articles proved to the satisfaction of the Collector not to have been produced in Bangladesh: Provided further that the Government may, by notification in the official Gazette, vary the rate at which customs duty shall be levied. (2) The Government may, by notification in the official Gazette, fix for the purposes of levying the said duty tariff values of any articles included in the Schedule, and may alter any tariff values for the time being in force.