Stamp duty query

Hello,

I would like to know stamp duty to be paid for a contract that is being signed in Mumbai but the client is in Delhi. How much stamp duty should we pay for the contract? Do we have to pay stamp duty in Mumbai or Delhi? 

This contract is for SaaS (Software as a Service)  for a period of 24 months with sales of X amount for development of product. 

Any help would be appreciated.

Thanks