Mr. Happy is the new registered owner of Unit B of 6/F and roof of Big Building which is a 6-storey domestic tenement building completed in 1962. The roof has a 45m covered structure erected and is currently leased to a tenant at a monthly rent of $13,000, inclusive of rates and management fees. One week ago, Mr. Happy received a Notice of Interim Valuation from the Commissioner of Rating and Valuation (CRV) of the Rating and Valuation Department (RVD). He claims that the roof structure is illegal and should not be included for the assessments of rates. He wishes to seek your advice on the following issues. (a) What is rateable value? Explain the assessment basis of rateable value under the Rating Ordinance (Cap.116). (b) Elaborate how the rateable value of the subject roof structure should be determined in this case. (c) What is the meaning of "tenement" under the Rating Ordinance (Cap.116),