Utility splitting between main floor tenants and basement tenants.

[Jishnu Pradeep]

The house has 3 different units. 1 in main floor and 2 in basement
Its a 3 BHK Main floor 7 students residing and 2 different 2 BHK basement units total 9 students resides .  

There is nothing written about the utilities division in the lease agreement for both parties.  But the practice for other house under same landlord is 60:40 split.

But here all the 3 different units has their own washing machine and dryer. eBill is 309$. As per 60:40 split, each one in basement pays 13$ and main floor pays 27%. How does that work, the main floor guys will have to pay for the washing done by basement guys.

In the other houses number of people in the basement is less and machines are shared, but here both are opposite. So i asked them to divide by total number of people and pay per head. that way the bill is 19$ per head. 

any suggestions please .