Scenario based SQL questions involving window functions

Ecommerce Data Mart Transaction -> Transaction_id, buyer_id, seller_id, object_id, Shipping_id, Price, Quantity, site_id transaction_date, expected_delivery_date, check_out_status leaf_category_id, defect_id Buyer -> Buyer_id, name, country Seller -> Seller_id, name, country, segment, standard Listing -> object_id, seller_id, auction_start_date auction_end_date, listing_site_id, leaf_category_id quantity 2) For the sellers from UK who transacted on the second week of december (6 December 2015 to 12 December 2015), find the number of sellers who have atleast twice the total transaction amount (qty*price) in the following week