Section 3(n) of the Act, as amended, excludes from the category of sales for resale “the sale of goods to be used in residential or farm building construction, repair or maintenance: Provided, That the sale is recognized as a bona fide retail sale in the industry.” Under this section a sale of building materials to a building contractor or a builder for use in residential or farm building, repair or maintenance is not a sale for resale, provided, the sale is otherwise recognized as a bona fide retail sale in the industry. If the sale is not so recognized it will be considered a sale for resale. Thus, only bona fide retail sales of building materials to a building contractor or a builder for the uses described would be taken out of the category of sales for resale. (Sucrs. De A. Mayol & Co. v. Mitchell, 280 F. 2d 477 (CA-1); Elder v. Phillips & Buttroff Mfg. Co., 23 L.C. Par. 67,524 (Tenn., 1958).) The legislative history of the amendment indicates that it is not the intent of its sponsors to remove from the category of sales for resale such sales, for example, as sales of lumber to a contractor to build a whole residential subdivision. (See 95 Cong. Rec. 12533-12535; Sen. St. ibid; 14877.)