Sra flat

ello sir, Please help Property details: SRA Flat, Andheri, Mumbai, 10 years will complete in june 2018, ie after 7 months 1) The SOCiety is Registered under Maharastra Co op Housing Society 2) Mr AMAR is Original Allotee : Share Certicate, Allotement letter dated 28 May 2008 , SRA Aggrement in his own Name ie Mr AMAR 3) First allotee/Owner ie Mr Amar sold the property to MRs Babita. by executing Sale of agreement, POWER OF ATTORNEY, AFFIDAVIT (Registered NOTARY ) on feb 2010. 4) Mrs Babita has transfer the reliance Electricity Bill flat in her own name. after purchase. 5) Mrs Babita expired on feb 2011 without "WILL". leaving behind 3 sons Mr X ( missing but his wife is avaible) , Mr. Y and Mr. Z 6) The Avaible 2 sons ie Mr Y And Mr Z, want to sell the SRA flat because of family dispute 7) Mr Chetan ie the 3 party purchase this flat from this two sons of the late Mrs Babita by executing Sale of agreement, POWER OF ATTORNEY, AFFIDAVIT (Registered NOTARY ) on sep 2017. So my Query is from Mr Chetan 1) What all steps need to do / documents required by Mr CHETAN(Third party) need to do from the 2 sons so that in future Ownership can be easily transfered in Mr CHETANS NAME 2) Can stamp Duty and registration can be paid and share certificate and ownership of flat can be transferred in Mr chetans name 3) How much stamp duty and registration amount need to be paid by Mr Chetan coz this the second sale PLEASE kindly give your EXPERT ADVICE. THANKS YOU