(a) If a purchaser who gives a certificate stating that property is purchased for resale makes any use of the property other than retention, demonstration, or display while holding it for sale in the regular course of business, the use shall be deemed a retail sale by the purchaser as of the time the property is first used by him and the cost of the property to him shall be deemed the gross receipts from the retail sale. If the sole use of the property other than retention, demonstration, or display in the regular course of business is the rental of the property while holding it for sale or the transportation of persons for hire while holding the property for sale, the purchaser may elect to include in his gross receipts either the amount of the rental charged or the total amount of the charges made by him for the transportation rather than the cost of the property to him.

(b) If a person who engages in the business of processing, manufacturing, or converting industrial materials into articles of tangible personal property for sale, whether as custom-made or stock items, makes any use of the article of tangible personal property other than retaining, demonstrating, or displaying it for sale, the use shall be deemed a retail sale as of the time the article is first used by him and its fair market value at the time shall be deemed the sales price of the article. If the sole use of the article other than retaining, demonstrating, or displaying it for sale is the rental of the article while holding it for sale, the processor, manufacturer, or converter may elect to treat the amount of the rental charged rather than the fair market value of the article as its sales price.