This question is probably better suited in the Business category, but I can help you. The FOB destination mean I, the seller, retain the ownership of the items until they reach you. The FOB shipping point indicates that you buy them at the shipping point, they are now yours, and are responsible for the shipping and arrival on your side of the shipment. The 3/10 and n/30 are discount terms.
My answer would be FOB shipping point because the problem states that Clothes R Us is required to be responsible for the shipping.