(a) loaded, unloaded or removed to any place for security, examination, weighing, sorting or any other purpose prior to delivery or, in the case of goods for export, to exportation, then all such operations shall be performed by or at the expense of the owner of the goods;

(b) unpacked, sorted, piled or otherwise prepared for examination, then all such operations shall be performed by and at the expense of the owner of the goods and in such manner as the proper officer may require so as to enable him to examine and take account of the goods.