Property Partition to 3 Brother - How is property value decided?

Scenario: A home is owned by three brothers - A, B and C. The home is individual house on 2700 Square feet of land with 2 floors (Ground floor and first floor both are of equal floor area) in Kolkata City. Family of "A" resides in Ground Floor rooms and Family of "C" resides in First Floor Rooms. "B" was away for 30 years and now back with his Family and wants to stay in the house. However, the house has two floors , One Bath and Kitchen in each floor. Water tank and pipeline are separate in two floors. Moreover, the building plan was sanctioned for two floors only, hence, we cannot construct 3rd floor.Hence, we have a problem to partition the house into 3. Now, Three brothers seat together and trying to evaluate, How much "A" and "C" has to pay to "B" so that "B" can take the money and settle somewhere else. Conflicts: 1. "B" claims 1/3 rd of value of entire Property, Whereas "A" and "C" deny because "B" did not pay maintenance of building in last 30 years. 2. "A" claims that "C" has to pay more to "B" than that of "A" , because property value of first floor is more than that of ground floor. "C" does not agree because built quality of first floor is poor and he has to climb up stair with having arthritis in his legs. If He has more pain to stay at first floor why should he pay more. Questions to lawyers: 1. How to determine which brother to pay how much if "B" stays away in this case? 2. Is the Claim of "A" valid that First floor valuation is more than ground floor Even we see first floor rooms are dilapidated? 3. How to resolve if the conflicts cannot be settled by verbal discussions.