Interpretation  PART 2  General  The combined area  The combined fire and rescue authority  Financial provision  ( a ) 2011 c. 13.  3 (2) The amount payable by the existing authorities is to be determined by apportioning the costs  of the Authority between the existing authorities in the proportion to the council tax base of each  authority.  5. —(1) The Hampshire Fire and Rescue Authority and the Isle of Wight Fire and Rescue  Authority (“the existing authorities”) must meet the costs of the Authority incurred for the purpose  of bringing the Scheme into full operation on 1st April 2021.  4. —(1) There is constituted as a fire and rescue authority for the combined area a body corporate  to be known as the Hampshire and Isle of Wight Fire and Rescue Authority.  (2) The Authority is constituted in accordance with the provisions of Part 3 of this Scheme.  3.  The combined area is the areas of Hampshire County Council, Isle of Wight Council,  Portsmouth City Council and Southampton City Council.  2.  In this Scheme—  “the Authority” means the fire and rescue authority constituted in accordance with paragraph  4;  “the 2011 Act” means the Police Reform and Social Responsibility Act 2011( a );  “constituent authority” means Hampshire County Council, Isle of Wight Council, Portsmouth  City Council and Southampton City Council;  “relevant police and crime commissioner” means a police and crime commissioner—  (a) whose area is the same as, or contains all of, the area of the Authority, or  (b) all or part of whose area falls within the area of the authority.  (a) constituting the Hampshire and Isle of Wight Fire and Rescue Authority as the fire and  rescue authority, and  (b) the performance by that authority of any functions necessary for bringing the scheme  fully into force on 1st April 2021.  (2) The scheme comes into force for all other purposes, on 1st April 2021. 