Seniority of merged partnership firm

Adityan A (Chartered Accountant) (27 Points)

31 July 2018  

'A' sole proprietorship CA firm established in 2010 and 'B' sole proprietorship CA firm established in 2016 are going to be merged into a partnership firm. Regarding seniority of the Merged Partnership firm, is it from 2010 or 2016 or 2018?