'Contract ' is defined in section 2(b) as meaning any agreement for carrying out for cash or 85 valuable consideration, the construction, fitting out, improvement or repair of any building, road, bridge or other immovable property; and 'goods ' are defined in section 2(d) as including "all materials, articles and commodities, whether or not to be used in the construction, fitting out, improvement or repair of immovable property." 'Sale price ' is defined in section 2(h)(ii) as meaning the amount payable to a dealer as valuable consideration for the carrying out of any contract, less such portion as may be prescribed, of such amount representing the usual proportion of the cost of labour to the cost of materials used in carrying out such contract. 'Dealer ' is defined in section 2(c) as meaning any person who sells or supplies any goods including goods sold or supplied in the execution of a contract.