Responsibility of individual flat electric meter connection in a builder flat

Sir, i recently purchased a builder flat in chatarpur area and shifted on 10 th june '24, there are 10 flats in the building, of which 9 are occupied and the last one would soon be , the builder has a common meter with sanctioned load of 1 kwthr, we have received an electricity bill of 86000 approximately, although there are sub- meters in the building for each flat but are not sanctioned by the authority so the bill is calculated as 1 st 182 units @ 3.50 next 183 @ 4.50 next 364 @ 6.50 next 365 @ 7 and the remaining 3499 units @ 8 now, if the meters were sanctioned individually then each would have to pay according to above calculations then these 10 flats would receive 182*10= 1820 units @ 3.50 = 6370 next 183*10=1830 units @ 4.50 = 8235 remaing 943 units @ 6.50 = 6129 this amount to = 20734 but at present the bill amounts to 86000 - clearly a huge difference now my question is 1. whose responsibility it is to get independent meter connections- the bulder or the person who has purchased the flat. 2. who must legally bear the extra electricity bill until the meters are connected in the name of owner. there are further questions that depend on answers of above questions